Flow Problem HDU - 3549 Dinic

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

2
3 2
1 2 1
2 3 1
3 3
1 2 1
2 3 1
1 3 1

Sample Output

Case 1: 1
Case 2: 2

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<cmath>
#include<vector>
#include<queue>
using namespace std;
typedef long long ll;
const int inf = 0x3f3f3f3f;
const int M = 1e5 + 10;
int t;
int n,m;
struct node
{
    int to,cap,rev;
};
vector<node>e[1100];//圖的鄰接表表示
int level[1100];//頂點到源點的距離標號
int iter[1100];//當前弧，在其之前的邊沒用
//增加一條從l到r容量爲c的邊
void init(int l,int r,int c)
{
    e[l].push_back((node){r,c,e[r].size()});
    e[r].push_back((node){l,0,e[l].size()-1});
}
//通過bfs計算從源點出發的距離標號
void bfs(int s)
{
    memset(level,-1,sizeof(level));
    queue<int>q;
    level[s]=0;
    q.push(s);
    while(!q.empty())
    {
        int v=q.front();
        q.pop();
        for(int i=0;i<e[v].size();i++)
        {
            node &ee=e[v][i];
           // cout<<ee.to<<" "<<ee.cap<<" "<<level[ee.to]<<" "<<level[v]+1<<endl;
            if(ee.cap>0&&level[ee.to]<0)
            {
                level[ee.to]=level[v]+1;
                q.push(ee.to);
            }
        }
    }
}
//通過dfs尋找增廣路
int dfs(int v,int t,int f)
{
    if(v==t)
        return f;
    for(int &i=iter[v];i<e[v].size();i++)
    {
        node &ee=e[v][i];
        if(ee.cap>0&&level[v]<level[ee.to])
        {
            int d=dfs(ee.to,t,min(f,ee.cap));
            if(d>0)
            {
                //cout<<d<<"*"<<endl;
                ee.cap-=d;
                e[ee.to][ee.rev].cap+=d;
                return d;
            }
        }
    }
    return 0;
}
int max_flow(int s,int t)
{
    int ff=0;
    for(;;)
    {
        bfs(s);

        if(level[t]<0)
            return ff;
        //cout<<s<<" "<<t<<endl;
        memset(iter,0,sizeof(iter));
        int f;
        while((f=dfs(s,t,inf))>0){
            ff+=f;
        }
    }
}
int main()
{
    scanf("%d",&t);
    int k=1;
    while(t--)
    {
        memset(e,0,sizeof(e));
        scanf("%d%d",&n,&m);
        int l,r,c;
        for(int i=0;i<m;i++)
        {
            scanf("%d%d%d",&l,&r,&c);
            init(l,r,c);
        }
        int ans=max_flow(1,n);
        printf("Case %d: %d\n",k++,ans);
    }
    return 0;
}