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  • HDU 3605 Escape

    Escape

    题解:如果一个人一条边和适应星球连一条流量为1的边,那么结果因为点数太多,边数太多而TLE。现在我们把所有的适应星球状态一样的人放在一起,然后在同一个状态的人的边一起连边,从而减少边数和点数。

    代码:

      1 #include<bits/stdc++.h>
      2 using namespace std;
      3 #define Fopen freopen("_in.txt","r",stdin); freopen("_out.txt","w",stdout);
      4 #define LL long long
      5 #define ULL unsigned LL
      6 #define fi first
      7 #define se second
      8 #define pb emplace_back
      9 #define lson l,m,rt<<1
     10 #define rson m+1,r,rt<<1|1
     11 #define lch(x) tr[x].son[0]
     12 #define rch(x) tr[x].son[1]
     13 #define max3(a,b,c) max(a,max(b,c))
     14 #define min3(a,b,c) min(a,min(b,c))
     15 typedef pair<int,int> pll;
     16 const int inf = 0x3f3f3f3f;
     17 const LL INF = 0x3f3f3f3f3f3f3f3f;
     18 const LL mod =  (int)1e9+7;
     19 const int N = 1024 + 100;
     20 const int M = N * 100;
     21 int head[N], deep[N], cur[N];
     22 int w[M], to[M], nx[M];
     23 int tot;
     24 void add(int u, int v, int val){
     25     w[tot]  = val; to[tot] = v;
     26     nx[tot] = head[u]; head[u] = tot++;
     27 
     28     w[tot] = 0; to[tot] = u;
     29     nx[tot] = head[v]; head[v] = tot++;
     30 }
     31 int bfs(int s, int t){
     32     queue<int> q;
     33     memset(deep, 0, sizeof(deep));
     34     q.push(s);
     35     deep[s] = 1;
     36     while(!q.empty()){
     37         int u = q.front();
     38         q.pop();
     39         for(int i = head[u]; ~i; i = nx[i]){
     40             if(w[i] > 0 && deep[to[i]] == 0){
     41                 deep[to[i]] = deep[u] + 1;
     42                 q.push(to[i]);
     43             }
     44         }
     45     }
     46     return deep[t] > 0;
     47 }
     48 int Dfs(int u, int t, int flow){
     49     if(u == t) return flow;
     50     for(int &i = cur[u]; ~i; i = nx[i]){
     51         if(deep[u]+1 == deep[to[i]] && w[i] > 0){
     52             int di = Dfs(to[i], t, min(w[i], flow));
     53             if(di > 0){
     54                 w[i] -= di, w[i^1] += di;
     55                 return di;
     56             }
     57         }
     58     }
     59     return 0;
     60 }
     61 
     62 int Dinic(int s, int t){
     63     int ans = 0, tmp;
     64     while(bfs(s, t)){
     65         for(int i = 0; i <= t; i++) cur[i] = head[i];
     66         while(tmp = Dfs(s, t, inf)) ans += tmp;
     67     }
     68     return ans;
     69 }
     70 int a[N];
     71 void init(){
     72     memset(head, -1, sizeof(head));
     73     memset(a, 0, sizeof(a));
     74     tot = 0;
     75 }
     76 int main(){
     77     int n, m;
     78     while(~scanf("%d%d", &n, &m)){
     79         init();
     80         int Max = (1 << m)- 1, val;
     81         for(int i = 1; i <= n; ++i){
     82             int tmp = 0;
     83             for(int i = 1; i <= m; ++i){
     84                 scanf("%d", &val);
     85                 tmp = tmp * 2 + val;
     86             }
     87             ++a[tmp];
     88         }
     89         int s = 0, t = Max + m + 1;
     90         for(int i = 1; i <= m; ++i){
     91             scanf("%d", &val);
     92             add(i + Max, t, val);
     93         }
     94         for(int i = 1; i <= Max; ++i){
     95             add(s, i, a[i]);
     96             for(int j = 1; j <= m; ++j){
     97                 if((i>>(m-j))&1) {
     98                     add(i, j+Max, inf);
     99                 }
    100             }
    101         }
    102         if(Dinic(s,t) == n) puts("YES");
    103         else puts("NO");
    104     }
    105     return 0;
    106 }
    View Code
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  • 原文地址:https://www.cnblogs.com/MingSD/p/9737160.html
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