[网络流24题]最小路径覆盖问题

最小路径覆盖模板题

#include<iostream>
#include<cstdio>
#include<cstring>
#include<vector>
#define maxn 155
#define maxm 6005
using namespace std;
int n,m;
struct edge{
    int from;
    int to;
    int next;
}E[maxm];
int sz=0;
int head[maxn];
void add_edge(int u,int v){
    sz++;
    E[sz].from=u;
    E[sz].to=v;
    E[sz].next=head[u];
    head[u]=sz;
}

int vis[maxn*2];
int match[maxn*2];
int dfs(int x){
    for(int i=head[x];i;i=E[i].next){
        int y=E[i].to;
        if(!vis[y]){
            vis[y]=1;
            if(!match[y]||dfs(match[y])){
                match[y]=x;
                match[x]=y;
                return 1;
            }
        }
    }
    return 0;
}

void print(int x){
    x+=n;
    do{
        x-=n;
        printf("%d ",x);
        vis[x]=1;
        x=match[x];
    }while(x!=0);
    printf("
"); 
}
int main(){
    int x,y;
    scanf("%d %d",&n,&m);
    for(int i=1;i<=m;i++){
        scanf("%d %d",&x,&y);
        add_edge(x,y+n); 
    }
    int ans=0;
    for(int i=1;i<=n;i++){
        memset(vis,0,sizeof(vis));
        if(dfs(i)) ans++;
    }
    memset(vis,0,sizeof(vis)); 
    for(int i=1;i<=n;i++){
        if(!vis[i]){
            print(i);
        }
    }
    printf("%d
",n-ans);
}