P3386 【模板】二分图最大匹配

#include<iostream>
#include<cstdio>
#include<queue>
#include<algorithm>
#include<cmath>
#include<ctime>
#include<set>
#include<map>
#include<stack>
#include<cstring>
#define inf 2147483647
#define ls rt<<1
#define rs rt<<1|1
#define lson ls,nl,mid,l,r
#define rson rs,mid+1,nr,l,r
#define N 1000010
#define For(i,a,b) for(long long i=a;i<=b;i++)
#define p(a) putchar(a)
#define g() getchar()

using namespace std;
long long n,m,x,y,v,k;

void in(long long &x){
    long long y=1;char c=getchar();x=0;
    while(c<‘0‘||c>‘9‘){if(c==‘-‘)y=-1;c=getchar();}
    while(c<=‘9‘&&c>=‘0‘){ x=(x<<1)+(x<<3)+c-‘0‘;c=getchar();}
    x*=y;
}
void o(long long x){
    if(x<0){p(‘-‘);x=-x;}
    if(x>9)o(x/10);
    p(x%10+‘0‘);
}

struct Dinic{
    long long maxflow,tot;
    long long head[N],deep[N],cur[N];
    queue<long long>q;

    struct node{
        long long n;
        long long v;
        long long next;
    }e[N];

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

    void push(long long x,long long y,long long v){
        e[tot].n=y;
        e[tot].v=v;
        e[tot].next=head[x];
        head[x]=tot++;
    }
    bool bfs(long long s,long long t){
        memset(deep,-1,sizeof(deep));
        For(i,0,n+m+2)
            cur[i]=head[i];
        deep[s]=0;
        q.push(s);
        while(!q.empty()){
            long long now=q.front();
            q.pop();
            for(long long i=head[now];i!=-1;i=e[i].next)
                if(deep[e[i].n]==-1 && e[i].v>0){
                    deep[e[i].n]=deep[now]+1;
                    q.push(e[i].n);
                }
        }
        return deep[t]!=-1;
    }

    long long dfs(long long now,long long t,long long lim){
        if(now==t||lim==0)
            return lim;
        long long flow=0,f;
        for(long long i=cur[now];i!=-1;i=e[i].next){
            cur[now]=i;
            if(deep[e[i].n]==deep[now]+1 && (f=dfs(e[i].n,t, min(lim,e[i].v) ))){
                flow+=f;
                lim-=f;
                e[i].v-=f;
                e[i^1].v+=f;
                if(!lim) break;
            }
        }
        return flow;
    }

    void dinic(long long s,long long t){
        while(bfs(s,t)){
            maxflow+=dfs(s,t,inf);
        }
    }
}g;

int main(){
    in(n);in(m);in(k);
    g.init();
    For(i,1,n){
        g.push(0,i,1);
        g.push(i,0,0);
    }
    For(i,1,m){
        g.push(i+n,n+m+1,1);
        g.push(n+m+1,n+i,0);
    }
    For(i,1,k){
        in(x);in(y);
        g.push(x,y+n,1);
        g.push(y+n,x,0);
    }
    g.dinic(0,n+m+1);
    o(g.maxflow);
    return 0;
}