最大流 Ford-Fulkerson算法

 1 #include <iostream>
 2 #include <stdio.h>
 3 #include <string.h>
 4 #include <vector>
 5 #define INF 0x3f3f3f3f
 6 using namespace std;
 7 const int MAX = 1010;
 8 struct Nod {
 9     int to, cap, rev;
10 };
11 vector<Nod> G[MAX];
12 bool vis[MAX];
13 void add_edge(int from, int to, int cap) {
14     G[from].push_back((Nod){to,cap,(int)G[to].size()});
15     G[to].push_back((Nod){from,0,(int)G[from].size()-1});
16 }
17 int dfs(int v, int t, int f) {
18     if(v == t) return f;
19     vis[v] = true;
20     for(int i = 0; i < G[v].size(); i ++) {
21         Nod &e = G[v][i];
22         if(!vis[e.to] && e.cap > 0) {
23             int d = dfs(e.to, t, min(f,e.cap));
24             if(d > 0) {
25                 e.cap -= d;
26                 G[e.to][e.rev].cap += d;
27                 return d;
28             }
29         }
30     }
31     return 0;
32 }
33 int max_flow(int s, int t){
34     int flow = 0;
35     while(1) {
36         memset(vis,0,sizeof(vis));
37         int f = dfs(s, t, INF);
38         if(f == 0) return flow;
39         flow += f;
40     }
41 }
42 int main() {
43     int t, n, m;
44     scanf("%d",&t);
45     for(int k = 1; k <= t; k ++) {
46         scanf("%d %d",&n, &m);
47         while(m--) {
48             int u, v, w;
49             scanf("%d %d %d",&u, &v, &w);
50             add_edge(u,v,w);
51         }
52         printf("Case %d: %d\n",k,max_flow(1,n));
53         for(int i = 1; i <= n; i ++) G[i].clear();
54     }
55     return 0;
56 }