URAL(timus) 1280 Topological Sorting(模拟)

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <time.h>
#include <string>
#include <map>
#include <stack>
#include <vector>
#include <set>
#include <queue>
#define inf 10000000
#define mod 10000
typedef long long ll;
using namespace std;
const int N=1005;
const int M=100005;
int power(int a,int b,int c){int ans=1;while(b){if(b%2==1){ans=(ans*a)%c;b--;}b/=2;a=a*a%c;}return ans;}
int in[N],vis[N],w[N][N];
int n,m,k;
vector<int>vec[N];

int main()
{
    int a,b;
    bool flag=true;
    scanf("%d%d",&n,&m);
    while(m--){
        scanf("%d%d",&a,&b);
        if(!w[a][b]){
            w[a][b]=1;
            vec[a].push_back(b);
        }
    }
    for(int i=1;i<=n;i++){
        scanf("%d",&in[i]);
    }
    for(int i=1;i<=n;i++){
        int cnt=0;
        for(int j=i+1;j<=n;j++){
            if(w[in[i]][in[j]])cnt++;
        }
    if(cnt!=vec[in[i]].size())flag=false;

    }
    if(flag)printf("YES\n");
    else printf("NO\n");
    return 0;
}