【模板】【网络流】Dinic

 /*
 唐代杜荀鹤
 《小松》
 自小刺头深草里，而今渐觉出蓬蒿。
 时人不识凌云木，直待凌云始道高。
 */
 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <cstring>
 #include <vector>
 #include <utility>
 #include <iomanip>
 #include <string>
 #include <cmath>
 #include <queue>
 #include <assert.h>
 #include <map>
 #include <ctime>
 #include <cstdlib>
 #include <stack>
 #include <set>
 #define LOCAL
 const int INF = 0x7fffffff;
 const int MAXN =   + ;
 const int maxnode =  *  +  * ;
 const int MAXM =  + ;
 const int MAX = ;
 using namespace std;
 struct Edge{
        int u, v, c, f;
        void init(int a, int b, int d, int e){
             u = a;v = b;
             c = d;f = e;
        }
 }edges[MAXM];
 int next[MAXN], M, cur[MAXN], vis[MAXN];
 int dist[MAXN], head[MAXN], n, m, sta, end;

 void addEdge(int u, int v, int c){
      edges[M].init(u, v, c, );M++;
      edges[M].init(v, u, , );//反向边
      next[M - ] = head[u];
      head[u] = M - ;
      next[M] = head[v];
      head[v] = M++;
      return;
 }
 void init(){
      M = ;//总边数
      memset(head, -, sizeof(head));
      scanf("%d%d", &n, &m);
      for (int i = ; i <= m; i++){
          int u, v, c;
          scanf("%d%d%d", &u, &v, &c);
          addEdge(u, v, c);
      }
      sta = ;
      end = n;
 }
 bool bfs(){
      memset(vis, , sizeof(vis));
      queue<int>Q;
      dist[sta] = ;
      vis[sta] = ;
      Q.push(sta);
      while (!Q.empty()){
            int u = Q.front();
            Q.pop();
            for (int i = head[u]; i != -;  i = next[i]){
                int e = i, v = edges[e].v;
                if (vis[v]) continue;
                if (edges[e].c > edges[e].f){
                   vis[v] = ;
                   dist[v] = dist[u] + ;
                   Q.push(v);
                }
            }
      }
      return vis[end];
 }
 int dfs(int x, int a){
     if (x == end || a == ) return a;
     int flow = , f;
     if (cur[x] == -) cur[x] = head[x];
     for (int &i = cur[x]; i != -; i = next[i]){
         int e = i, v = edges[i].v;
         if (dist[v] == dist[x] +  && (f = dfs(v, min(edges[e].c - edges[e].f, a))) > ){
            flow += f;
            a -= f;
            edges[e].f += f;
            edges[e ^ ].f -= f;
            if (a == ) break;
         }
     }
     return flow;
 }
 int Dinic(){
     int flow = ;
     while (bfs()){
           memset(cur, -, sizeof(cur));
           flow += dfs(sta, INF);
     }
     return flow;
 }

 int main(){
    #ifdef LOCAL
    freopen("data.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
    #endif
    init();
    printf("%d", Dinic());
    //printf("%d", (a == c));
    return ;
 }