HDU 3549 Flow Problem

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Flow Problem

Time Limit: 5000/5000 MS (Java/Others)    Memory Limit: 65535/32768 K (Java/Others)
Total Submission(s): 7865    Accepted Submission(s): 3659

Problem 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
题意很简单 ，就是一个简单的最大流问题，模板直接过。。。作为一个新手刚学 表示理解的还是不怎么深刻，跟龙哥调了一上午也没发现错在哪。。啥都不说了，都是泪啊 上代码
#include <iostream>#include <queue>#include <string.h>#include <stdio.h>#include <stdlib.h>#define N 25#define MAX 9999999using namespace std;int n,m;int vis[N];int map1[N][N],pre[N];int bfs(int s,int e){    memset(vis, 0, sizeof(vis));    memset(pre,-1,sizeof(pre));    pre[s]=0;    vis[s]=MAX;    queue<int>q;    q.push(s);    while(!q.empty())    {        int k = q.front();        q.pop();        if(k==e) break;        for(int i=1; i<=n; i++)        {            if(map1[k][i]>0 && pre[i]==-1)            {                pre[i] = k;                vis[i] = min(map1[k][i],vis[k]);       //一开始while外了，也没错就是交不上，后来放着居然就A了                q.push(i);            }        }    }    if(pre[e]==-1)        return -1;    return vis[e];}int zuida(int s,int e){    int ans=0;    while(1)    {        int y = bfs(s,e);        if(y == -1)  break;        for(int i = n; i != 1; i = pre[i])        {            map1[pre[i]][i] -= y;            map1[i][pre[i]] += y;        }        ans+=y;    }    return ans;}int main(){    int T;    int Case = 1;    scanf("%d",&T);    while(T--)    {        memset(map1,0,sizeof(map1));        scanf("%d%d",&n,&m);        for(int i=1; i<=m; i++)        {            int a,b,c;            scanf("%d%d%d",&a,&b,&c);            map1[a][b]+= c;        }        int ans=zuida(1, n);        cout<<"Case "<<Case++<<": ";        printf("%d\n",ans);    }    return 0;}