dinic 最大流模板

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#include<bits/stdc++.h>
using namespace std;
const int Ni = 2000005;
const int MAX = 1<<26;
struct Edge{
    int u,v,c;
    int next;
}edge[3*Ni];
int n,m,cnt,head[Ni],d[Ni],sp,tp;//原点，汇点

void add(int u,int v,int c){
    edge[cnt].u=u; edge[cnt].v=v; edge[cnt].c=c;
    edge[cnt].next=head[u]; head[u]=cnt++;

    edge[cnt].u=v; edge[cnt].v=u; edge[cnt].c=0;
    edge[cnt].next=head[v]; head[v]=cnt++;
}
int bfs(){
    queue <int> q;
    memset(d,-1,sizeof(d));
    d[sp]=0;
    q.push(sp);
    while(!q.empty()){
        int cur=q.front();
        q.pop();
        for(int i=head[cur];i!=-1;i=edge[i].next){
            int u=edge[i].v;
            if(d[u]==-1 && edge[i].c>0){
                d[u]=d[cur]+1;
                q.push(u);
            }
        }
    }
    return d[tp] != -1;
}
int dfs(int a,int b){
    int r=0;
    if(a==tp)return b;
    for(int i=head[a];i!=-1 && r<b;i=edge[i].next)
    {
        int u=edge[i].v;
        if(edge[i].c>0 && d[u]==d[a]+1)
        {
            int x=min(edge[i].c,b-r);
            x=dfs(u,x);
            r+=x;
            edge[i].c-=x;
            edge[i^1].c+=x;
        }
    }
    if(!r)d[a]=-2;
    return r;
}

int dinic(int sp,int tp){
    int total=0,t;
    while(bfs()){
        while(t=dfs(sp,MAX))
        total+=t;
    }
    return total;
}
int main(){
    int i,u,v,c,x;
    while(~scanf("%d%d",&n,&m)){
        cnt=0;
        memset(head,-1,sizeof(head));
        sp=1,tp=n*m;

        printf("%d\n",dinic(sp,tp));
    }
    return 0;
}