网络流

#include <cstdio>
#include <iostream>
#include <cstring>
#include <ctime>
#include <cstdlib>
#include <vector>
#include <stack>
#include <algorithm>
#include <map>
#include <queue>
using namespace std;
#define ll long long
const int maxn=210;
const int maxm=210;
ll ma[maxn][maxn];
bool vis[maxn];
int pre[maxn],n,m;;
ll get_path(int s,int t)
{
    for(int i=0; i<maxn; i++)vis[i]=0,pre[i]=-1;
    queue<int>que;
    que.push(s);
    vis[s]=1;
    ll res=1e9;
    while(que.size())
    {
        int x=que.front();
        que.pop();
        for(int i=1; i<=n; i++)
        {
            if(vis[i]==0&&ma[x][i]!=0)
            {
                vis[i]=1;
                pre[i]=x;
                res=min(res,ma[x][i]);
                que.push(i);
                if(i==t)return res;//到达终点
            }
        }
    }
    return 0;//无法到达终点
}
void updata(int t,int add)//更新边
{
    int i=t;
    while(pre[i]!=-1)
    {
        ma[pre[i]][i]-=add;
        ma[i][pre[i]]+=add;
        i=pre[i];
    }
}
int main()
{

    while(cin>>m>>n)
    {
        memset(ma,0,sizeof(ma));
        for(int i=1; i<=m; i++)
        {
            ll a,b,c;
            scanf("%lld %lld %lld",&a,&b,&c);
            ma[a][b]+=c;
        }
        ll ans=0;
        while(1)
        {
            int add=get_path(1,n);
            if(add==0)break;
            updata(n,add);
            ans+=add;
        }
        cout<<ans<<endl;
    }
    return 0;
}