dinic模板

　　注意pos和head都初始化为-1

M要开两倍  因为连双向边

stnm都开局部变量即可

#include<bits/stdc++.h>
using namespace std;
//input by bxd
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define repp(i,a,b) for(int i=(a);i>=(b);--i)
#define RI(n) scanf("%d",&(n))
#define RII(n,m) scanf("%d%d",&n,&m)
#define RIII(n,m,k) scanf("%d%d%d",&n,&m,&k)
#define RS(s) scanf("%s",s);
#define ll long long
#define pb push_back
#define REP(i,N)  for(int i=0;i<(N);i++)
#define CLR(A,v)  memset(A,v,sizeof A)
//////////////////////////////////
#define inf 0x3f3f3f3f
const int N=10000+5;
const int M=200000+5;
int head[M],pos;
struct Edge
{
    int to,nex=-1,v;
}edge[M];
void init()
{
    pos=-1;
    CLR(head,-1);
}
void add(int a,int b,int c)
{
    edge[++pos].nex=head[a];
    head[a]=pos;
    edge[pos].to=b;
    edge[pos].v=c;
    edge[++pos].nex=head[b];
    head[b]=pos;
    edge[pos].to=a;
    edge[pos].v=0;
}

int deth[N];
int bfs(int s,int t)
{
    CLR(deth,0);
    queue<int>q;
    deth[s]=1;
    q.push(s);
    while(!q.empty())
    {
        int u=q.front();q.pop();
        for(int i=head[u];i!=-1;i=edge[i].nex)
        {
            int v=edge[i].to;
            if(edge[i].v>0&&deth[v]==0)
            {
                deth[v]=deth[u]+1;
                q.push(v);
            }
        }
    }
    return deth[t];
}
int dfs(int s,int t,int dis)
{
    if(s==t)return dis;
    for(int i=head[s];i!=-1;i=edge[i].nex)
    {
        int v=edge[i].to;
        if(deth[v]==deth[s]+1&&edge[i].v!=0)
        {
            int di=dfs(v,t,min(dis,edge[i].v));
            if(di>0)
            {
                edge[i].v-=di;
                edge[i^1].v+=di;
                return di;
            }
        }
    }
    return 0;
}

int dinic(int s,int t)
{
    int ans=0;
    while(bfs(s,t))
        while(int di=dfs(s,t,inf))
        ans+=di;
    return ans;
}

int main()
{
    int n,m,s,t;
    RII(n,m);
    RII(s,t);
    init();
    while(m--)
    {
        int a,b,c;RIII(a,b,c);
        add(a,b,c);
    }
    cout<<dinic(s,t);
}

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