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  • 【 2013 Multi-University Training Contest 1 】

    HDU 4602 Partition

    f[i]表示和为i的方案数。已知f[i]=2i-1

    dp[i]表示和为i,k有多少个。那么dp[i]=dp[1]+dp[2]+...+dp[i-1]+f[i-k]。

    考虑与f有关的项:

    f[n-k]是答案的一部分,即2n-k-1是答案的一部分。

    把与dp有关的项:

    令s[i-1]=dp[1]+dp[2]+...+dp[i-1],那么s[n-1]是答案的一部分。

    s[i]=s[i-1]+dp[i],又dp[i]=s[i-1]+f[i-k]。推出s[i]=2*s[i-1]+f[i-k],dp[k]=s[k]=1。

    可以推出s[n-1]=2n-k-1+(n-k-1)*2n-k-2

     1 #include<iostream>
     2 typedef long long LL;
     3 LL MOD = 1000000007LL;
     4 using namespace std;
     5 LL powmod(LL a, LL b) {
     6     LL ans;
     7     a %= MOD;
     8     for (ans = 1; b; b >>= 1) {
     9         if (b & 1) {
    10             ans *= a;
    11             ans %= MOD;
    12         }
    13         a *= a;
    14         a %= MOD;
    15     }
    16     return ans;
    17 }
    18 int main() {
    19     int T;
    20     LL n, k;
    21     LL ans;
    22     cin >> T;
    23     while (T--) {
    24         cin >> n >> k;
    25         if (k > n) {
    26             ans = 0;
    27         } else if (k == n) {
    28             ans = 1;
    29         } else if (n - k == 1) {
    30             ans = 2;
    31         } else if (n - k == 2) {
    32             ans = 5;
    33         } else {
    34             ans = powmod(2, n - k - 1)
    35                     + (n - k - 1) * powmod(2, n - k - 2) % MOD;
    36             ans += powmod(2, n - k - 1);
    37             ans = (ans % MOD + MOD) % MOD;
    38         }
    39         cout << ans << endl;
    40     }
    41     return 0;
    42 }
    View Code

    HDU 4604 Deque

    枚举第i个数,假设它最早出现且在队列里,那么以i为起点的最长非降子序列一定在队列里(push_back),以i为起点的最长非升子序列也一定在队列里(push_front)。

     1 #include<cstdio>
     2 #include<algorithm>
     3 #define MAXN 100010
     4 #define oo 123456789
     5 using namespace std;
     6 int arr[MAXN];
     7 int up[MAXN], down[MAXN], cnt[MAXN];
     8 int st[MAXN], top;
     9 void LIS(int n, int dp[]) {
    10     int i;
    11     int pos;
    12     top = -1;
    13     for (i = 0; i < n; i++) {
    14         if (top < 0 || st[top] <= arr[i]) {
    15             st[++top] = arr[i];
    16             dp[i] = top + 1;
    17         } else {
    18             pos = upper_bound(st, st + top + 1, arr[i]) - st;
    19             st[pos] = arr[i];
    20             dp[i] = pos + 1;
    21         }
    22         cnt[i] = min(cnt[i],
    23                 upper_bound(st, st + top + 1, arr[i])
    24                         - lower_bound(st, st + top + 1, arr[i]));
    25     }
    26 }
    27 int main() {
    28     int T;
    29     int n;
    30     int i;
    31     int ans;
    32     scanf("%d", &T);
    33     while (T--) {
    34         scanf("%d", &n);
    35         for (i = 0; i < n; i++) {
    36             scanf("%d", &arr[i]);
    37             cnt[i] = oo;
    38         }
    39         reverse(arr, arr + n);
    40         LIS(n, up);
    41         for (i = 0; i < n; i++) {
    42             arr[i] = -arr[i];
    43         }
    44         LIS(n, down);
    45         ans = 0;
    46         for (i = 0; i < n; i++) {
    47             ans = max(ans, up[i] + down[i] - cnt[i]);
    48         }
    49         printf("%d
    ", ans);
    50     }
    51     return 0;
    52 }
    View Code

    HDU 4605 Magic Ball Game

    统计树上一个节点到根,权值大于/小于某个数的个数:数状数组/线段树。

    离线处理询问,对所有w的值离散化。

    从树根开始DFS,第一次到达一个节点时,回答所有询问。

    向儿子DFS时,更新往左/右的数状数组。

    最后一次离开一个节点时,还原现场。

      1 #pragma comment(linker, "/STACK:1024000000,1024000000")
      2 
      3 #include<cstdio>
      4 #include<cstring>
      5 #include<algorithm>
      6 #include<vector>
      7 #include<set>
      8 #define MAXN 200010
      9 using namespace std;
     10 int w[MAXN], tmp[MAXN];
     11 struct node {
     12     int pre;
     13     int next[2];
     14     void init() {
     15         pre = -1;
     16         next[0] = next[1] = -1;
     17     }
     18 } tree[MAXN];
     19 struct Ask {
     20     int weight;
     21     int pos;
     22 };
     23 vector<Ask> q[MAXN];
     24 pair<int, int> res[MAXN];
     25 bool stop[MAXN];
     26 multiset<int> myset;
     27 inline int lowbit(int x) {
     28     return x & -x;
     29 }
     30 void update(int arr[], int i, int val) {
     31     for (; i < MAXN; i += lowbit(i)) {
     32         arr[i] += val;
     33     }
     34 }
     35 int sum(int arr[], int i) {
     36     int ans;
     37     for (ans = 0; i > 0; i -= lowbit(i)) {
     38         ans += arr[i];
     39     }
     40     return ans;
     41 }
     42 int left[MAXN], right[MAXN];
     43 void dfs(int x) {
     44     int i, j;
     45     for (i = 0; i < (int) q[x].size(); i++) {
     46         j = q[x][i].pos;
     47         if (myset.count(q[x][i].weight)) {
     48             res[j].first = -1;
     49         } else {
     50             res[j].first = sum(right, q[x][i].weight - 1);
     51             res[j].second = 3 * sum(left, q[x][i].weight - 1)
     52                     + 3 * sum(right, q[x][i].weight - 1);
     53 
     54             res[j].second += sum(left, MAXN - 1) - sum(left, q[x][i].weight);
     55             res[j].second += sum(right, MAXN - 1) - sum(right, q[x][i].weight);
     56         }
     57     }
     58 
     59     myset.insert(w[x]);
     60     if (tree[x].next[0] != -1) {
     61         update(left, w[x], 1);
     62         dfs(tree[x].next[0]);
     63         update(left, w[x], -1);
     64     }
     65     if (tree[x].next[1] != -1) {
     66         update(right, w[x], 1);
     67         dfs(tree[x].next[1]);
     68         update(right, w[x], -1);
     69     }
     70     myset.erase(myset.find(w[x]));
     71 }
     72 int main() {
     73     int T;
     74     int n, m;
     75     int i, j;
     76     int u, a, b;
     77     int size;
     78     Ask ask;
     79     scanf("%d", &T);
     80     while (T--) {
     81         scanf("%d", &n);
     82         size = 0;
     83         for (i = 1; i <= n; i++) {
     84             scanf("%d", &w[i]);
     85             tree[i].init();
     86             q[i].clear();
     87             tmp[size++] = w[i];
     88         }
     89         scanf("%d", &m);
     90         while (m--) {
     91             scanf("%d%d%d", &u, &a, &b);
     92             tree[u].next[0] = a;
     93             tree[u].next[1] = b;
     94             tree[a].pre = u;
     95             tree[b].pre = u;
     96         }
     97         scanf("%d", &m);
     98         for (i = 0; i < m; i++) {
     99             scanf("%d%d", &u, &ask.weight);
    100             ask.pos = i;
    101             q[u].push_back(ask);
    102             tmp[size++] = ask.weight;
    103         }
    104         sort(tmp, tmp + size);
    105         size = unique(tmp, tmp + size) - tmp;
    106         for (i = 1; i <= n; i++) {
    107             w[i] = lower_bound(tmp, tmp + size, w[i]) - tmp + 1;
    108             for (j = 0; j < (int) q[i].size(); j++) {
    109                 q[i][j].weight = lower_bound(tmp, tmp + size, q[i][j].weight)
    110                         - tmp + 1;
    111             }
    112         }
    113         myset.clear();
    114         memset(left, 0, sizeof(left));
    115         memset(right, 0, sizeof(right));
    116         for (i = 1; i <= n; i++) {
    117             if (tree[i].pre < 0) {
    118                 dfs(i);
    119                 break;
    120             }
    121         }
    122         for (i = 0; i < m; i++) {
    123             if (res[i].first < 0) {
    124                 puts("0");
    125             } else {
    126                 printf("%d %d
    ", res[i].first, res[i].second);
    127             }
    128         }
    129     }
    130     return 0;
    131 }
    View Code

    HDU 4606 Occupy Cities

    预处理出任意两个城市的最短距离。

    若士兵可以从一个城市i到达另一个城市j,且i比j先占领,才连i->j的边。

    二分士兵背包的容量,可以得到一个有向图。二分条件是有向图的最小路径覆盖与士兵人数的关系。

      1 #include<cstdio>
      2 #include<cstring>
      3 #include<algorithm>
      4 #include<cmath>
      5 #define MAXN 310
      6 #define MAXM 10010
      7 #define oo 123456789
      8 #define eps 1e-6
      9 using namespace std;
     10 
     11 struct point {
     12     double x, y;
     13 };
     14 struct line {
     15     point a, b;
     16 };
     17 point city[MAXN];
     18 line barr[MAXN];
     19 
     20 double dis[MAXN][MAXN];
     21 int first[MAXM], next[MAXM], v[MAXM], e;
     22 int order[MAXN];
     23 int cx[MAXN], cy[MAXN];
     24 bool mk[MAXN];
     25 
     26 int dbcmp(double x, double y) {
     27     if (fabs(x - y) < eps) {
     28         return 0;
     29     } else {
     30         return x > y ? 1 : -1;
     31     }
     32 }
     33 bool zero(double x) {
     34     return fabs(x) < eps;
     35 }
     36 double dist(point p1, point p2) {
     37     return sqrt((p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) * (p1.y - p2.y));
     38 }
     39 double xmult(point p1, point p2, point p0) {
     40     return (p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y);
     41 }
     42 int dots_inline(point p1, point p2, point p3) {
     43     return zero(xmult(p1, p2, p3));
     44 }
     45 int same_side(point p1, point p2, line l) {
     46     return xmult(l.a, p1, l.b) * xmult(l.a, p2, l.b) > eps;
     47 }
     48 int same_side(point p1, point p2, point l1, point l2) {
     49     return xmult(l1, p1, l2) * xmult(l1, p2, l2) > eps;
     50 }
     51 inline int dot_online_in(point p, point l1, point l2) {
     52     return zero(xmult(p, l1, l2)) && (l1.x - p.x) * (l2.x - p.x) < eps
     53             && (l1.y - p.y) * (l2.y - p.y) < eps;
     54 }
     55 int dot_online_in(point p, line l) {
     56     return zero(xmult(p, l.a, l.b)) && (l.a.x - p.x) * (l.b.x - p.x) < eps
     57             && (l.a.y - p.y) * (l.b.y - p.y) < eps;
     58 }
     59 int intersect_in(point u1, point u2, point v1, point v2) {
     60     if (!dots_inline(u1, u2, v1) || !dots_inline(u1, u2, v2))
     61         return !same_side(u1, u2, v1, v2) && !same_side(v1, v2, u1, u2);
     62     return dot_online_in(u1, v1, v2) || dot_online_in(u2, v1, v2)
     63             || dot_online_in(v1, u1, u2) || dot_online_in(v2, u1, u2);
     64 }
     65 
     66 void floyd(int n) {
     67     int i, j, k;
     68     for (k = 0; k < n; k++) {
     69         for (i = 0; i < n; i++) {
     70             for (j = 0; j < n; j++) {
     71                 dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
     72             }
     73         }
     74     }
     75 }
     76 inline void addEdge(int x, int y) {
     77     v[e] = y;
     78     next[e] = first[x];
     79     first[x] = e++;
     80 }
     81 int path(int x) {
     82     int y;
     83     for (int i = first[x]; i != -1; i = next[i]) {
     84         y = v[i];
     85         if (!mk[y]) {
     86             mk[y] = true;
     87             if (cy[y] == -1 || path(cy[y])) {
     88                 cx[x] = y;
     89                 cy[y] = x;
     90                 return 1;
     91             }
     92         }
     93     }
     94     return 0;
     95 }
     96 int match(int n) {
     97     int res, i;
     98     memset(cx, -1, sizeof(cx));
     99     memset(cy, -1, sizeof(cy));
    100     for (res = i = 0; i < n; i++) {
    101         if (cx[i] == -1) {
    102             memset(mk, false, sizeof(mk));
    103             res += path(i);
    104         }
    105     }
    106     return res;
    107 }
    108 int main() {
    109     int T;
    110     int n, m, p;
    111     int i, j, k;
    112     double low, high, mid;
    113     scanf("%d", &T);
    114     while (T--) {
    115         scanf("%d%d%d", &n, &m, &p);
    116         for (i = 0; i < n; i++) {
    117             scanf("%lf%lf", &city[i].x, &city[i].y);
    118         }
    119         for (i = 0; i < m; i++) {
    120             scanf("%lf%lf%lf%lf", &barr[i].a.x, &barr[i].a.y, &barr[i].b.x,
    121                     &barr[i].b.y);
    122         }
    123         for (i = 0; i < n; i++) {
    124             scanf("%d", &order[i]);
    125             order[i]--;
    126         }
    127 
    128         for (i = 0; i < n + m + m; i++) {
    129             for (j = 0; j <= i; j++) {
    130                 dis[i][j] = dis[j][i] = oo;
    131             }
    132         }
    133 
    134         for (i = 0; i < n; i++) {
    135             dis[i][i] = 0;
    136             for (j = i + 1; j < n; j++) {
    137                 for (k = 0; k < m; k++) {
    138                     if (intersect_in(city[i], city[j], barr[k].a, barr[k].b)) {
    139                         break;
    140                     }
    141                 }
    142                 if (k >= m) {
    143                     dis[i][j] = dis[j][i] = dist(city[i], city[j]);
    144                 }
    145             }
    146         }
    147 
    148         for (i = 0; i < n; i++) {
    149             for (j = 0; j < m; j++) {
    150                 for (k = 0; k < m; k++) {
    151                     if (j == k) {
    152                         continue;
    153                     }
    154                     if (intersect_in(city[i], barr[j].a, barr[k].a,
    155                             barr[k].b)) {
    156                         break;
    157                     }
    158                 }
    159                 if (k >= m) {
    160                     dis[i][n + (j << 1)] = dis[n + (j << 1)][i] = dist(city[i],
    161                             barr[j].a);
    162                 }
    163                 for (k = 0; k < m; k++) {
    164                     if (j == k) {
    165                         continue;
    166                     }
    167                     if (intersect_in(city[i], barr[j].b, barr[k].a,
    168                             barr[k].b)) {
    169                         break;
    170                     }
    171                 }
    172                 if (k >= m) {
    173                     dis[i][n + (j << 1 | 1)] = dis[n + (j << 1 | 1)][i] = dist(
    174                             city[i], barr[j].b);
    175                 }
    176 
    177             }
    178         }
    179 
    180         for (i = 0; i < m; i++) {
    181             for (j = 0; j < i; j++) {
    182                 for (k = 0; k < m; k++) {
    183                     if (k == i || k == j) {
    184                         continue;
    185                     }
    186                     if (intersect_in(barr[i].a, barr[j].a, barr[k].a,
    187                             barr[k].b)) {
    188                         break;
    189                     }
    190                 }
    191                 if (k >= m) {
    192                     dis[n + (i << 1)][n + (j << 1)] = dis[n + (j << 1)][n
    193                             + (i << 1)] = dist(barr[i].a, barr[j].a);
    194                 }
    195 
    196                 for (k = 0; k < m; k++) {
    197                     if (k == i || k == j) {
    198                         continue;
    199                     }
    200                     if (intersect_in(barr[i].a, barr[j].b, barr[k].a,
    201                             barr[k].b)) {
    202                         break;
    203                     }
    204                 }
    205                 if (k >= m) {
    206                     dis[n + (i << 1)][n + (j << 1 | 1)] =
    207                             dis[n + (j << 1 | 1)][n + (i << 1)] = dist(
    208                                     barr[i].a, barr[j].b);
    209                 }
    210 
    211                 for (k = 0; k < m; k++) {
    212                     if (k == i || k == j) {
    213                         continue;
    214                     }
    215                     if (intersect_in(barr[i].b, barr[j].a, barr[k].a,
    216                             barr[k].b)) {
    217                         break;
    218                     }
    219                 }
    220                 if (k >= m) {
    221                     dis[n + (i << 1 | 1)][n + (j << 1)] = dis[n + (j << 1)][n
    222                             + (i << 1 | 1)] = dist(barr[i].b, barr[j].a);
    223                 }
    224 
    225                 for (k = 0; k < m; k++) {
    226                     if (k == i || k == j) {
    227                         continue;
    228                     }
    229                     if (intersect_in(barr[i].b, barr[j].b, barr[k].a,
    230                             barr[k].b)) {
    231                         break;
    232                     }
    233                 }
    234                 if (k >= m) {
    235                     dis[n + (i << 1 | 1)][n + (j << 1 | 1)] = dis[n
    236                             + (j << 1 | 1)][n + (i << 1 | 1)] = dist(barr[i].b,
    237                             barr[j].b);
    238                 }
    239             }
    240         }
    241 
    242         floyd(n + m + m);
    243 
    244         low = 0;
    245         high = oo;
    246         while (dbcmp(low, high) < 0) {
    247             e = 0;
    248             memset(first, -1, sizeof(first));
    249             mid = (low + high) * 0.5;
    250             for (i = 0; i < n; i++) {
    251                 for (j = i + 1; j < n; j++) {
    252                     if (dbcmp(dis[order[i]][order[j]], mid) <= 0) {
    253                         addEdge(order[i], order[j]);
    254                     }
    255                 }
    256             }
    257             if (n - match(n) > p) {
    258                 low = mid;
    259             } else {
    260                 high = mid;
    261             }
    262         }
    263 
    264         printf("%.2lf
    ", mid);
    265 
    266     }
    267     return 0;
    268 }
    View Code

    HDU 4607 Park Visit

    最长链上的边走一次,其他边都必须走两次。

    dp[i][0]表示以i为根的子树的最大深度,dp[i][1]表示以i为根的子树的次大深度。

    答案就是max(dp[i][0]+dp[i][1])。

     1 #include<cstdio>
     2 #include<cstring>
     3 #include<algorithm>
     4 #define MAXN 200010
     5 using namespace std;
     6 int first[MAXN], next[MAXN], v[MAXN], e;
     7 int dp[MAXN][2];
     8 bool vis[MAXN];
     9 inline void addEdge(int x, int y) {
    10     v[e] = y;
    11     next[e] = first[x];
    12     first[x] = e++;
    13 }
    14 void dfs(int x) {
    15     vis[x] = true;
    16     dp[x][0] = dp[x][1] = 0;
    17     for (int i = first[x]; i != -1; i = next[i]) {
    18         int y = v[i];
    19         if (!vis[y]) {
    20             dfs(y);
    21             if (dp[y][0] + 1 >= dp[x][0]) {
    22                 dp[x][1] = dp[x][0];
    23                 dp[x][0] = dp[y][0] + 1;
    24             } else if (dp[y][0] + 1 >= dp[x][1]) {
    25                 dp[x][1] = dp[y][0] + 1;
    26             }
    27         }
    28     }
    29 }
    30 int main() {
    31     int T;
    32     int n, m;
    33     int i;
    34     int x, y;
    35     scanf("%d", &T);
    36     while (T--) {
    37         scanf("%d%d", &n, &m);
    38         e = 0;
    39         memset(first, -1, sizeof(first));
    40         for (i = 1; i < n; i++) {
    41             scanf("%d%d", &x, &y);
    42             addEdge(x, y);
    43             addEdge(y, x);
    44         }
    45         memset(vis, false, sizeof(vis));
    46         dfs(1);
    47         x = 0;
    48         for (i = 1; i <= n; i++) {
    49             x = max(x, dp[i][0] + dp[i][1]);
    50         }
    51         while (m--) {
    52             scanf("%d", &y);
    53             if (y <= x + 1) {
    54                 printf("%d
    ", y - 1);
    55             } else {
    56                 printf("%d
    ", x + 2 * (y - x - 1));
    57             }
    58         }
    59     }
    60     return 0;
    61 }
    View Code

    HDU 4608  I-number

    因为y不会比x大多少,所以直接高精度加法暴力。

     1 #include<cstdio>
     2 #include<cstring>
     3 #include<algorithm>
     4 #define MAXN 200010
     5 using namespace std;
     6 int digit[MAXN];
     7 char str[MAXN];
     8 int main() {
     9     int T;
    10     int i;
    11     int len;
    12     int sum;
    13     scanf("%d", &T);
    14     while (T--) {
    15         scanf(" %s", str);
    16         len = strlen(str);
    17         memset(digit, 0, sizeof(digit));
    18         for (i = 0; str[i]; i++) {
    19             digit[i] = str[i] - '0';
    20         }
    21         reverse(digit, digit + len);
    22         while (1) {
    23             digit[0]++;
    24             sum = 0;
    25             for (i = 0; i < len; i++) {
    26                 if (digit[i] > 9) {
    27                     digit[i] -= 10;
    28                     digit[i + 1]++;
    29                     if (i == len - 1) {
    30                         len++;
    31                     }
    32                 }
    33                 sum += digit[i];
    34             }
    35             if (sum % 10 == 0) {
    36                 break;
    37             }
    38         }
    39         for (i = len - 1; i >= 0; i--) {
    40             printf("%d", digit[i]);
    41         }
    42         putchar('
    ');
    43     }
    44     return 0;
    45 }
    View Code

    HDU 4609 3-idiots

    对于多项式乘法,普通做法需要O(n2)的时间复杂度。

    而FFT仅需要O(nlogn)的时间复杂度。

    把三角形边长作为多项式的指数,边长的出现次数作为多项式的系数。

    把两个多项式相乘,即可得到任意两边长之和(i)出现的次数(num[i])。

    由于一条边只能使用一次,所以num[arr[i]+arr[i]]--。

    由于“先a后b”与“先b后a”属于同一种方案,所以num[i]>>=1。

    不妨假设a<=b<=c,要构成三角形只要满足a+b>c。

    由于a+b>c不容易统计,但是a+b<=c的方案数很容易统计,枚举c就可以做到。

      1 #include<cstdio>
      2 #include<cstring>
      3 #include<cmath>
      4 #include<algorithm>
      5 #define MAXN 400010
      6 #define EPS 1e-8
      7 typedef long long LL;
      8 using namespace std;
      9 double PI = acos(-1.0);
     10 int arr[MAXN];
     11 LL num[MAXN], sum[MAXN];
     12 struct complex {
     13     double r, i;
     14     complex(double _r = 0, double _i = 0) {
     15         r = _r;
     16         i = _i;
     17     }
     18     complex operator+(const complex &b) {
     19         return complex(r + b.r, i + b.i);
     20     }
     21     complex operator-(const complex &b) {
     22         return complex(r - b.r, i - b.i);
     23     }
     24     complex operator*(const complex &b) {
     25         return complex(r * b.r - i * b.i, r * b.i + i * b.r);
     26     }
     27 };
     28 complex x[MAXN];
     29 void change(complex y[], int len) {
     30     for (int i = 1, j = len >> 1; i < len - 1; i++) {
     31         if (i < j) {
     32             swap(y[i], y[j]);
     33         }
     34         int k = len >> 1;
     35         for (; j >= k; k >>= 1) {
     36             j -= k;
     37         }
     38         if (j < k) {
     39             j += k;
     40         }
     41     }
     42 }
     43 void FFT(complex y[], int len, int on) {
     44     change(y, len);
     45     for (int h = 2; h <= len; h <<= 1) {
     46         complex wn(cos(-on * 2 * PI / h), sin(-on * 2 * PI / h));
     47         for (int j = 0; j < len; j += h) {
     48             complex w(1, 0);
     49             for (int k = j; k < j + (h >> 1); k++) {
     50                 complex u = y[k];
     51                 complex t = w * y[k + (h >> 1)];
     52                 y[k] = u + t;
     53                 y[k + (h >> 1)] = u - t;
     54                 w = w * wn;
     55             }
     56         }
     57     }
     58     if (on == -1) {
     59         for (int i = 0; i < len; i++) {
     60             y[i].r /= len;
     61         }
     62     }
     63 }
     64 int main() {
     65     int T;
     66     int n;
     67     int len, len1;
     68     double ans;
     69     scanf("%d", &T);
     70     while (T--) {
     71         memset(num, 0, sizeof(num));
     72         scanf("%d", &n);
     73         for (int i = 0; i < n; i++) {
     74             scanf("%d", &arr[i]);
     75             num[arr[i]]++;
     76         }
     77         sort(arr, arr + n);
     78         len1 = arr[n - 1] + 1;
     79         for (len = 1; len <= (len1 << 1); len <<= 1)
     80             ;
     81         for (int i = 0; i < len1; i++) {
     82             x[i] = complex(num[i], 0);
     83         }
     84         for (int i = len1; i < len; i++) {
     85             x[i] = complex(0, 0);
     86         }
     87         FFT(x, len, 1);
     88         for (int i = 0; i < len; i++) {
     89             x[i] = x[i] * x[i];
     90         }
     91         FFT(x, len, -1);
     92         for (int i = 0; i < len; i++) {
     93             num[i] = (LL) (x[i].r + 0.5 + EPS);
     94         }
     95         for (int i = 0; i < n; i++) {
     96             num[arr[i] + arr[i]]--;
     97         }
     98         for (int i = 0; i < len; i++) {
     99             num[i] >>= 1;
    100         }
    101         sum[0] = 0;
    102         for (int i = 1; i < len; i++) {
    103             sum[i] = sum[i - 1] + num[i];
    104         }
    105         ans = 0;
    106         for (int i = 0; i < n; i++) {
    107             ans += sum[arr[i]];
    108         }
    109         printf("%.7lf
    ", 1 - ans * 6 / (n * (n - 1.0) * (n - 2.0)));
    110     }
    111     return 0;
    112 }
    View Code

    4610 Cards

    通过筛素数可以快速判定素数。

    条件1,条件2可以快速解决;

    条件3,一个数约数之和可能大于该数的好几倍;

    条件4,一个数约束的乘积可能爆longlong,要通过分解素因子,判是否是平方数。

    由于N的总数不超过20000,N个数的范围都在106内,所以可以O(sqrt(n))的复杂度处理出约数。

    由于条件只有4个,所以K个数中,只有24=16个不同种类的数。因此可以枚举每种数是否出现216,贪心的选择。

      1 #include<cstdio>
      2 #include<cstring>
      3 #include<vector>
      4 #include<algorithm>
      5 #include<map>
      6 #define oo 987654321
      7 #define MAXP 5000010
      8 #define MAXN 1000010
      9 #define MAXM 4
     10 typedef long long LL;
     11 using namespace std;
     12 bool p[MAXP];
     13 int num[1 << MAXM];
     14 int satisfy[MAXN];
     15 int add[MAXM];
     16 vector<int> prime;
     17 void init() {
     18     int i, j;
     19     memset(p, true, sizeof(p));
     20     p[0] = p[1] = false;
     21     for (i = 2; i * i < MAXP; i++) {
     22         if (p[i]) {
     23             for (j = i * i; j < MAXP; j += i) {
     24                 p[j] = false;
     25             }
     26         }
     27     }
     28     for (i = 2; i < MAXP; i++) {
     29         if (p[i]) {
     30             prime.push_back(i);
     31         }
     32     }
     33 }
     34 bool isSquare(int val, int cnt, int flag) {
     35     map<int, int> mymap;
     36     int i;
     37     for (i = 0; prime[i] * prime[i] <= val; i++) {
     38         while (val % prime[i] == 0) {
     39             mymap[prime[i]]++;
     40             val /= prime[i];
     41         }
     42     }
     43     if (val > 1) {
     44         mymap[val]++;
     45     }
     46     map<int, int>::iterator it;
     47     for (it = mymap.begin(); it != mymap.end(); it++) {
     48         (*it).second *= cnt;
     49     }
     50     for (i = 0; prime[i] * prime[i] <= flag; i++) {
     51         while (flag % prime[i] == 0) {
     52             mymap[prime[i]]++;
     53             flag /= prime[i];
     54         }
     55     }
     56     if (flag > 1) {
     57         mymap[flag]++;
     58     }
     59     for (it = mymap.begin(); it != mymap.end(); it++) {
     60         if ((*it).second & 1) {
     61             return false;
     62         }
     63     }
     64     return true;
     65 }
     66 void getSatisfy(int val) {
     67     if (satisfy[val] < 0) {
     68         int res = 0;
     69         int i;
     70         int amount = 0;
     71         int sum = 0;
     72         int product = 0;
     73         int flag = 1;
     74         for (i = 1; i * i < val; i++) {
     75             if (val % i == 0) {
     76                 amount += 2;
     77                 sum += i + val / i;
     78                 product++;
     79             }
     80         }
     81         if (i * i == val) {
     82             amount++;
     83             sum += i;
     84             flag = i;
     85         }
     86         if (p[val]) {
     87             res |= 1 << 0;
     88         }
     89         if (p[amount]) {
     90             res |= 1 << 1;
     91         }
     92         if (p[sum]) {
     93             res |= 1 << 2;
     94         }
     95         if (isSquare(val, product, flag)) {
     96             res |= 1 << 3;
     97         }
     98         satisfy[val] = res;
     99     }
    100 }
    101 int numOfOne(int val) {
    102     int res;
    103     for (res = 0; val; val >>= 1) {
    104         res += val & 1;
    105     }
    106     return res;
    107 }
    108 bool cmp(int x, int y) {
    109     return numOfOne(x) > numOfOne(y);
    110 }
    111 int main() {
    112     int T;
    113     int n, k;
    114     int i, j;
    115     int tmp, cnt;
    116     int ans, res;
    117     int sum;
    118     bool flag;
    119     vector<int> g;
    120     init();
    121     memset(satisfy, -1, sizeof(satisfy));
    122     scanf("%d", &T);
    123     while (T--) {
    124         memset(num, 0, sizeof(num));
    125         scanf("%d%d", &n, &k);
    126         for (i = 0; i < n; i++) {
    127             scanf("%d%d", &tmp, &cnt);
    128             getSatisfy(tmp);
    129             num[satisfy[tmp]] += cnt;
    130 
    131             printf("%d", numOfOne(satisfy[tmp]));
    132             if (i < n - 1) {
    133                 putchar(' ');
    134             } else {
    135                 putchar('
    ');
    136             }
    137         }
    138         for (i = 0; i < MAXM; i++) {
    139             scanf("%d", &add[i]);
    140         }
    141         ans = -oo;
    142         for (i = 0; i < (1 << (1 << MAXM)); i++) {
    143             g.clear();
    144             for (tmp = i, j = 0; tmp; tmp >>= 1, j++) {
    145                 if (tmp & 1) {
    146                     g.push_back(j);
    147                 }
    148             }
    149             if ((int) g.size() > k) {
    150                 continue;
    151             }
    152             flag = true;
    153             sum = 0;
    154             tmp = 0;
    155             for (j = 0; flag && j < (int) g.size(); j++) {
    156                 if (num[g[j]] <= 0) {
    157                     flag = false;
    158                 }
    159                 sum += num[g[j]];
    160                 tmp |= g[j];
    161             }
    162             if (flag && sum >= k) {
    163                 sort(g.begin(), g.end(), cmp);
    164                 res = 0;
    165                 for (j = 0; j < MAXM; j++, tmp >>= 1) {
    166                     if (!(tmp & 1)) {
    167                         res += add[j];
    168                     }
    169                 }
    170                 for (j = 0; j < (int) g.size(); j++) {
    171                     res += numOfOne(g[j]);
    172                 }
    173                 tmp = k - g.size();
    174                 for (j = 0; tmp && j < (int) g.size(); j++) {
    175                     cnt = min(tmp, num[g[j]] - 1);
    176                     res += cnt * numOfOne(g[j]);
    177                     tmp -= cnt;
    178                 }
    179                 ans = max(ans, res);
    180             }
    181         }
    182         printf("%d
    ", ans);
    183     }
    184     return 0;
    185 }
    View Code
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  • 原文地址:https://www.cnblogs.com/DrunBee/p/3209212.html
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