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  • 2018.10.07模拟总结

    国庆5天乐在今天终于结束了,怀着明天又得上学的心情,我开始写这篇题解。

    T1 wzoi

      期望得分:100

      实际得分:100

      首先题面非常的迷,我看了十分钟都没懂,看完T2,T3后再回来看T1,总共看题看了20分钟才懂……

      我发现最优的答案一定是回文串,那么ans = 10 * (len / 2),于是为了维护这个,我就开了个栈,如果栈是空的或者栈顶元素和当前数字不同,就放入栈,否则就把栈顶元素弹出,加10分。最后栈中要么不剩,要么一定是偶数个,加上5 * num / 2即可。

      总的来说就是贪心,正确性其实我也不太确定,但是手出的数据都过了……

     1 #include<cstdio>
     2 #include<iostream>
     3 #include<cmath>
     4 #include<algorithm>
     5 #include<cstring>
     6 #include<cstdlib>
     7 #include<cctype>
     8 #include<vector>
     9 #include<stack>
    10 #include<queue>
    11 using namespace std;
    12 #define enter puts("") 
    13 #define space putchar(' ')
    14 #define Mem(a, x) memset(a, x, sizeof(a))
    15 #define rg register
    16 typedef long long ll;
    17 typedef double db;
    18 const int INF = 0x3f3f3f3f;
    19 const db eps = 1e-8;
    20 const int maxn = 1e6 + 5;
    21 inline ll read()
    22 {
    23     ll ans = 0;
    24     char ch = getchar(), last = ' ';
    25     while(!isdigit(ch)) {last = ch; ch = getchar();}
    26     while(isdigit(ch)) {ans = ans * 10 + ch - '0'; ch = getchar();}
    27     if(last == '-') ans = -ans;
    28     return ans;
    29 }
    30 inline void write(ll x)
    31 {
    32     if(x < 0) x = -x, putchar('-');
    33     if(x >= 10) write(x / 10);
    34     putchar(x % 10 + '0');
    35 }
    36 void MYFILE()
    37 {
    38 #ifndef mrclr
    39   freopen("wzoi.in", "r", stdin);
    40   freopen("wzoi.out", "w", stdout);
    41 #endif
    42 }
    43 
    44 int n;
    45 char c[maxn];
    46 int a[maxn];
    47 int st[maxn], sc = 0;
    48 int ans = 0;
    49 
    50 int main()
    51 {
    52   MYFILE();
    53   scanf("%s", c + 1);
    54   n = strlen(c + 1);
    55   for(int i = 1; i <= n; ++i) a[i] = c[i] - '0';
    56   for(int i = 1; i <= n; ++i)
    57     {
    58       if(!sc || st[sc] != a[i]) st[++sc] = a[i];
    59       else ans += 10, sc--;
    60     }
    61   if(sc) ans += 5 * (sc >> 1);
    62   write(ans); enter;
    63   return 0;
    64 }
    View Code

    T2 course

      期望得分:10

      实际得分:40

      这题实在不会,开始搞10%的暴力:枚举全排列,然后判断是否合法,如果合法,在O(nm)判断单词是否是一个子串,记录个数。复杂度O(n! * n2 * m)。

      对于大的数,固输0.000000.

      然后成绩下来后也是惊了:0的点竟然有三个,净赚30.

      标程说出来可能不信:随机 +暴力判断。按题中描述可知,这些点构成一个森林,然后对于每一层的拓扑序,直接随机选哪个根节点,这样就得到了一个序列,剩下的就和暴力一样了。

      Ssy大佬直接随机序列,连判断都没有,竟然期望得分80~100……果然tql。

    放一个考场40分的代码吧

     1 #include<cstdio>
     2 #include<iostream>
     3 #include<cmath>
     4 #include<algorithm>
     5 #include<cstring>
     6 #include<cstdlib>
     7 #include<cctype>
     8 #include<vector>
     9 #include<stack>
    10 #include<queue>
    11 using namespace std;
    12 #define enter puts("") 
    13 #define space putchar(' ')
    14 #define Mem(a, x) memset(a, x, sizeof(a))
    15 #define rg register
    16 typedef long long ll;
    17 typedef double db;
    18 const int INF = 0x3f3f3f3f;
    19 const db eps = 1e-8;
    20 const int maxn = 20;
    21 inline ll read()
    22 {
    23     ll ans = 0;
    24     char ch = getchar(), last = ' ';
    25     while(!isdigit(ch)) {last = ch; ch = getchar();}
    26     while(isdigit(ch)) {ans = ans * 10 + ch - '0'; ch = getchar();}
    27     if(last == '-') ans = -ans;
    28     return ans;
    29 }
    30 inline void write(ll x)
    31 {
    32     if(x < 0) x = -x, putchar('-');
    33     if(x >= 10) write(x / 10);
    34     putchar(x % 10 + '0');
    35 }
    36 void MYFILE()
    37 {
    38 #ifndef mrclr
    39   freopen("course.in", "r", stdin);
    40   freopen("course.out", "w", stdout);
    41 #endif
    42 }
    43 
    44 int n, m, pre[maxn], t[maxn];
    45 char c[maxn], no[6][21], New[maxn];
    46 bool vis[maxn];
    47 
    48 bool judge()
    49 {
    50   for(int i = 1; i <= n; ++i) vis[i] = 0;
    51   vis[0] = 1;
    52   for(int i = 1; i <= n; ++i)
    53     {
    54       if(!vis[pre[t[i]]]) return 0;
    55       vis[t[i]] = 1;
    56       New[i] = c[t[i]];
    57     }
    58   return 1;
    59 }
    60 void work0()
    61 {
    62   int tot = 0, totno = 0;
    63   do
    64     {
    65       if(judge())
    66     {
    67       tot++;
    68       for(int i = 1; i <= m; ++i)
    69         {
    70           bool flg = 0;
    71           int l = strlen(no[i] + 1);
    72           for(int j = 1; j <= n - l + 1; ++j)
    73         {
    74           bool flg2 = 1;
    75           for(int k = 1; k <= l; ++k)
    76             if(New[j + k - 1] != no[i][k]) {flg2 = 0; break;}
    77           if(flg2) {flg = 1; break;}
    78         }
    79           if(flg) {totno++; break;}
    80         }
    81     }
    82     }while(next_permutation(t + 1, t + n + 1));
    83   printf("%.6lf
    ", (db)(tot - totno) / (db)tot);
    84 }
    85 
    86 int main()
    87 {
    88   MYFILE();
    89   n = read();
    90   if(n > 18) {printf("0.000000
    "); return 0;}
    91   for(int i = 1; i <= n; ++i) pre[i] = read(), t[i] = i;
    92   scanf("%s", c + 1);
    93   m = read();
    94   for(int i = 1; i <= m; ++i) scanf("%s", no[i] + 1);
    95   work0();
    96   return 0;
    97 }
    View Code

    T3 painting

      期望得分:40

      实际得分:30

      这噶的更不会了!

      不过40分暴力想想还是能写出来的:把bfs的队列改成优先队列,每一次都从当前已经算出的最小的数向四个方向延伸,而且延伸出来的一定是w + d(w == wmin),因为对于任意一个w,一定有w + d >= wmin + d,说明这个点一定不是限制上限的点,为了最大化ans,就取w + d。

      丢了10分是因为没开long, long。(太zz了……)  

    正解:没看懂。

    40分代码

     1 #include<cstdio>
     2 #include<iostream>
     3 #include<cmath>
     4 #include<algorithm>
     5 #include<cstring>
     6 #include<cstdlib>
     7 #include<cctype>
     8 #include<vector>
     9 #include<stack>
    10 #include<queue>
    11 using namespace std;
    12 #define enter puts("") 
    13 #define space putchar(' ')
    14 #define Mem(a, x) memset(a, x, sizeof(a))
    15 #define rg register
    16 typedef long long ll;
    17 typedef double db;
    18 const int INF = 0x3f3f3f3f;
    19 const db eps = 1e-8;
    20 const int maxn = 1e3 + 5;
    21 const ll mod = 1e9 + 7;
    22 inline ll read()
    23 {
    24     ll ans = 0;
    25     char ch = getchar(), last = ' ';
    26     while(!isdigit(ch)) {last = ch; ch = getchar();}
    27     while(isdigit(ch)) {ans = ans * 10 + ch - '0'; ch = getchar();}
    28     if(last == '-') ans = -ans;
    29     return ans;
    30 }
    31 inline void write(ll x)
    32 {
    33     if(x < 0) x = -x, putchar('-');
    34     if(x >= 10) write(x / 10);
    35     putchar(x % 10 + '0');
    36 }
    37 void MYFILE()
    38 {
    39 #ifndef mrclr
    40   freopen("painting.in", "r", stdin);
    41   freopen("painting.out", "w", stdout);
    42 #endif
    43 }
    44 
    45 int n, m, k, d;
    46 ll mp[maxn][maxn], ans = 0;
    47 
    48 const int dx[] = {-1, 0, 1, 0}, dy[] = {0, 1, 0, -1};
    49 struct Node
    50 {
    51   int x, y;
    52   ll w;
    53   bool operator < (const Node &oth)const
    54   {
    55     return w > oth.w;
    56   }
    57 };
    58 priority_queue<Node> q;
    59 void bfs()
    60 {
    61   while(!q.empty())
    62     {
    63       Node now = q.top(); q.pop();
    64       ans += now.w; ans %= mod;
    65       for(int i = 0; i < 4; ++i)
    66     {
    67       int newx = now.x + dx[i], newy = now.y + dy[i];
    68       if(newx > 0 && newx <= n && newy > 0 && newy <= m)
    69         {
    70           if(mp[newx][newy])
    71         {
    72           if(mp[newx][newy] > now.w + d)
    73             {printf("IMPOSSIBLE
    "); return;}
    74         }
    75           else
    76         {
    77           mp[newx][newy] = now.w + d;
    78           q.push((Node){newx, newy, now.w + d});
    79         }
    80         }
    81     }
    82     }
    83   write(ans); enter;
    84 }
    85 
    86 int main()
    87 {
    88   MYFILE();
    89   n = read(); m = read(); k = read(); d = read();
    90   if(n > 1000 || m > 1000) {printf("IMPOSSIBLE
    "); return 0;}
    91   for(int i = 1; i <= k; ++i)
    92     {
    93       int x = read(), y = read(), w = read();
    94       mp[x][y] = w;
    95       q.push((Node){x, y, w});
    96     }
    97   bfs();
    98   return 0;
    99 }
    View Code

    总结一下:第一题送的,剩下两题暴力+固输 = 40 + 40,所以今天应该180起……

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  • 原文地址:https://www.cnblogs.com/mrclr/p/9750286.html
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