hdu3549 网络流ek模板

Description

Network flow is a well-known difficult problem for ACMers. Given a graph, your task is to find out the maximum flow for the weighted directed graph.

Input

The first line of input contains an integer T, denoting the number of test cases. 
For each test case, the first line contains two integers N and M, denoting the number of vertexes and edges in the graph. (2 <= N <= 15, 0 <= M <= 1000) 
Next M lines, each line contains three integers X, Y and C, there is an edge from X to Y and the capacity of it is C. (1 <= X, Y <= N, 1 <= C <= 1000)

Output

For each test cases, you should output the maximum flow from source 1 to sink N.

题意就是裸网络流，直接ek搞过去即可

#include<cstdio>#include<cstring>#include<algorithm>#include<iostream>#include<vector>#include<queue>using namespace std;const int inf=0x3f3f3f3f;int mp[20][20];int flow[20];int pre[20];int n,m;int st,ed;int bfs(){memset(pre,-1,sizeof(pre));//memset(flow,0,sizeof(flow));pre[st]=0;flow[st]=inf;queue<int> q;q.push(st);while(!q.empty()){int t=q.front();q.pop();if(t==ed) break;for(int i=1;i<=n;i++){if(i!=st&&pre[i]==-1&&mp[t][i]){pre[i]=t;flow[i]=min(flow[t],mp[t][i]);q.push(i);}}}if(pre[ed]!=-1) return flow[ed];else return -1;}int calc(){int pr,maxn=0,now,step;while((step=bfs())!=-1){maxn+=step;now=ed;while(now!=st){pr=pre[now];mp[pr][now]-=step;mp[now][pr]+=step;now=pr;}}return maxn;}int main(){int x,y,t,T,tt=0;scanf("%d",&T);while(T--){memset(mp,0,sizeof(mp));scanf("%d %d",&n,&m);for(int i=0;i<m;i++){scanf("%d %d %d",&x,&y,&t);mp[x][y]+=t;}st=1,ed=n;printf("Case %d: %d\n",++tt,calc());}return 0;}