hdu2647 Reward 拓扑排序

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N = 10100, M =20010;
struct node
{
    int to,  next;
};
node edge[M];
int ind[N], head[N],que[N],ans[N];
int iq,tot,t;
void topo(int n)
{
    int i,k,j=0,x,y;
    t=-1;x=0;
    for(i=1;i<=n;i++)
        if(ind[i]==0) que[j++]=i;
    ans[++t]=j-x;
    y=0;
    x=j;
    for(i=0;i<j;i++)
    {
        if(i==ans[t]+y)
        {
            ans[++t]=j-x;
            x=j;
            y=i;
        }

        int u=que[i];
        for(k=head[u]; k!=-1; k=edge[k].next)
        {
            ind[edge[k].to]--;
            if(ind[edge[k].to]==0)
                que[j++]=edge[k].to;
        }
    }
    iq=j;
}
void addedge(int i,int j)
{
    edge[tot].to=j;edge[tot].next=head[i];head[i]=tot++;
}
void init()
{
    tot=0;
    memset(ind,0,sizeof(ind));
    memset(head,-1,sizeof(head));
}
int main()
{
    //freopen("test.txt","r",stdin);
    int n,m,i,j,k;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        init();
        int flag=0;
        while(m--)
        {
            scanf("%d%d",&i,&j);
            if(i==j) flag=1;
            if(flag) continue;
            ind[i]++;
            addedge(j,i);
        }
        topo(n);
        if(iq<n||flag) printf("-1\n");
        else
        {
            int s=0;
            for(i=0;i<=t;i++) s+=ans[i]*(i+888);
            printf("%d\n",s);
        }
    }
    return 0;
}