網絡流Dinic算法

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>
#include <queue>
using namespace std;

const int MAXN = 210;
const int MAXM = 210*210;
const int INF = 0x3f3f3f3f;

struct Edge
{
    int v, f;
    int next;
}edge[MAXM];

int n, m;
int cnt;

int head[MAXN], level[MAXN];
int q[MAXN];

void init()
{
    cnt = 0;
    memset(head, -1, sizeof(head));
}

void read_graph(int u, int v, int f)
{
    edge[cnt].v = v, edge[cnt].f = f;
    edge[cnt].next = head[u], head[u] = cnt++;
    edge[cnt].v = u, edge[cnt].f = 0;  //增加一條反向弧，容量爲0 
    edge[cnt].next = head[v], head[v] = cnt++;
}

int bfs(int s, int t) //構建層次網絡 
{
    memset(level, 0, sizeof(level));
    level[s] = 1;
    int front = 0, rear = 1;
    q[front] = s;
    while(front < rear)
    {
        int x = q[front++];
        if(x == t) return 1;
        for(int e = head[x]; e != -1; e = edge[e].next)
        {
            int v = edge[e].v, f = edge[e].f;
            if(!level[v] && f)
            {
                level[v] = level[x] + 1;
                q[rear++] = v;
            }
        }
    }
    return 0;
}

int dfs(int u, int maxf, int t)
{
    if(u == t) return maxf;
    int ret = 0;
    for(int e = head[u]; e != -1; e = edge[e].next)
    {
        int v = edge[e].v, f = edge[e].f;
        if(level[u] + 1 == level[v] && f)
        {
            int Min = min(maxf-ret, f);
            f = dfs(v, Min, t);
            edge[e].f -= f;
            edge[e^1].f += f;
            ret += f;
            if(ret == maxf) return ret;
        }
    }
    return ret;
}

int Dinic(int s, int t) //Dinic
{
    int ans = 0;
    while(bfs(s, t)) ans += dfs(s, INF, t);
    return ans;
}

int main()
{
    int n,t;
    while(cin>>n>>t)
    {
        init();
        int u,v,f;
        while(n--)
        {
            cin>>u>>v>>f;
            read_graph(u,v,f);
        }
        cout<<Dinic(1,t)<<endl;
    }
    return 0;
}