洛谷 P3376 【模板】网络最大流

题目链接

保存一下dinic的板子 (不开longlong见祖宗）

#include <bits/stdc++.h>
using namespace std;
const int INF=0x7fffffff;
const int MAXN = 210,MAXM = 10010;
namespace maxflow {
    typedef long long type;
    const type INF=0x7fffffff;
    struct node {
        int to; type cap; int next;
        node(int t=0,type c=0,int n=0):to(t),cap(c),next(n) {};
    } edge[MAXM];
    int head[MAXN],tot;
    void addedge(int from,int to,type cap,type rcap=0) {
        edge[tot]=node(to,cap,head[from]); head[from]=tot++;
        edge[tot]=node(from,rcap,head[to]); head[to]=tot++;
    }
    int dep[MAXN],cur[MAXN];//当前弧优化
    bool bfs(int s,int t,int n) {
        static int Q[MAXN],ST,ED;
        memset(dep+1,0,n*sizeof(int));
        ST=0; ED=-1;
        Q[++ED]=s; dep[s]=1;
        while (ST<=ED) {
            int u=Q[ST++];
            for (int i=head[u]; i!=-1; i=edge[i].next) {
                int v=edge[i].to;
                if (!dep[v]&&edge[i].cap) {
                    Q[++ED]=v; dep[v]=dep[u]+1;
                }
            }
        } return (dep[t]!=0);
    }
    type dfs(int x,const int &t,type flow=INF) {
        if (x==t||flow==0) return flow;
        type ret=0;
        for (int i=cur[x]; i!=-1; i=edge[i].next) {
            if (dep[x]+1==dep[edge[i].to]&&edge[i].cap){
                type f=dfs(edge[i].to,t,min(flow,edge[i].cap));
                edge[i].cap-=f; edge[i^1].cap+=f;
                ret+=f; flow-=f; cur[x]=i;
                if (flow==0) break;
            }
        } if (!ret) dep[x]=0;
        return ret;
    }
    type maxflow(int s,int t,int n) {//Dinic
        type ret=0;
        while (bfs(s,t,n)) {
            type f;
            memcpy(cur+1,head+1,n*sizeof(int));
            while ((f=dfs(s,t))>0) ret+=f;
        } return ret;
    }
    void init(int n) {
        memset(head+1,0xff,n*sizeof(int)); tot=0;
    }
}

int main(){
    int n,m,s,t;
    cin>>n>>m>>s>>t;
    maxflow::init(n);
    for(int i=0,u,v,w;i<m;i++){
        cin>>u>>v>>w;
        maxflow::addedge(u,v,w);
    }
    cout<<maxflow::maxflow(s,t,n)<<"\n";
    return 0;
}