hdu1532 （最大流入门，EK算法）
看着这个博客
然后敲了hdu1532这个入门题，算是对最大流有点理解了
1 #include <stdio.h> 2 #include <string.h> 3 #include <queue> 4 using namespace std; 5 const int INF = 1<<30; 6 const int N = 200 + 10; 7 int n,m; 8 int cap[N][N],flow[N],pre[N]; 9 int bfs(int src, int des)//每次用bfs找到最小的delta 10 { 11 queue<int> q; 12 for(int i=1;i<=n; ++i) 13 pre[i] = -1; 14 pre[src] = 0; 15 flow[src] = INF; 16 q.push(src); 17 while(!q.empty()) 18 { 19 int u = q.front(); q.pop(); 20 21 for(int i=1;i<=n;++i) 22 if(i!=src && cap[u][i]>0 && pre[i]==-1) 23 { 24 pre[i] = u; 25 flow[i] = min(cap[u][i],flow[u]); 26 q.push(i); 27 } 28 } 29 //printf("%d\n",pre[des]); 30 if(pre[des]==-1) 31 return -1; 32 else 33 return flow[des]; 34 } 35 int maxFlow(int src, int des) 36 { 37 int sumFlow = 0; 38 int add = 0; 39 while((add = bfs(src,des)) != -1)//如果不为-1，那么就进行增广 40 { 41 int k = des; 42 while(k!=src) 43 { 44 int fa = pre[k]; 45 cap[fa][k] -= add; 46 cap[k][fa] += add; 47 k = fa; 48 } 49 sumFlow += add; 50 } 51 return sumFlow; 52 53 } 54 int main() 55 { 56 57 while(scanf("%d%d",&m,&n)!=EOF) 58 { 59 int u,v,c; 60 memset(cap,0,sizeof(cap)); 61 for(int i=1;i<=m;++i) 62 { 63 scanf("%d%d%d",&u,&v,&c); 64 cap[u][v] += c; 65 66 } 67 int ans = maxFlow(1,n); 68 printf("%d\n",ans); 69 } 70 return 0; 71 }
