HDU3549--最大流水题

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.

 

Sample Input

23 21 2 12 3 13 31 2 12 3 11 3 1

 

Sample Output

Case 1: 1Case 2: 2

#include <iostream>#include <cstdio>#include <queue>using namespace std;#define maxn 18#define inf 0x7fffffffint cap[maxn][maxn];int pre[maxn];bool val[maxn];int n;inline int min(int a,int b){return a>b?b:a;}bool bfs(int s,int t){memset(val,0,sizeof(val));val[s]=1;queue <int> q;q.push(s);while(!q.empty()){int p=q.front();q.pop();for(int i=1;i<=n;i++){if(cap[p][i]>0&&!val[i]){val[i]=1;pre[i]=p;q.push(i);if(i==t){return true;}}}}return false;}int EK(int s,int t){int flow=0;while(bfs(s,t)){int d=inf;for(int i=t;i!=s;i=pre[i]){d=min(d,cap[pre[i]][i]);}for(int i=t;i!=s;i=pre[i]){cap[i][pre[i]]+=d;cap[pre[i]][i]-=d;}flow+=d;}return flow;}int main(){int t,m;scanf("%d",&t);for(int i=1;i<=t;i++){scanf("%d%d",&n,&m);memset(cap,0,sizeof(cap));for(int j=1;j<=m;j++){int u,v,w;scanf("%d%d%d",&u,&v,&w);cap[u][v]+=w;}printf("Case %d: ",i);printf("%d\n",EK(1,n));}return 0;}