1280. Topological Sorting

http://acm.timus.ru/problem.aspx?space=1&num=1280

水题

代码：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<vector>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<algorithm>
#include<cmath>

using namespace std;
//#pragma comment(linker,"/STACK:1000000000,1000000000")

#define LL long long

const int INF=0x3f3f3f3f;
const int N=1005;
const int M=100005;
int head[N],I;
struct node
{
    int j,next;
}side[M];
int a[N];
int num[N];
void Add(int i,int j)
{
    side[I].j=j;
    side[I].next=head[i];
    head[i]=I++;
}
int main()
{
    int n,m;
    while(scanf("%d %d",&n,&m)!=EOF)
    {
        memset(head,-1,sizeof(head));
        I=0;
        memset(num,0,sizeof(num));
        while(m--)
        {
            int i,j;
            scanf("%d %d",&i,&j);
            ++num[j];
            Add(i,j);
        }
        for(int i=0;i<n;++i)
        scanf("%d",&a[i]);
        int l;
        for(l=0;l<n;++l)
        {
            if(num[a[l]])
            break;
            for(int t=head[a[l]];t!=-1;t=side[t].next)
            --num[side[t].j];
        }
        if(l<n)
        printf("NO\n");
        else
        printf("YES\n");
    }
    return 0;
}