hdu 2647拓扑排序 容器

#include<stdio.h>

#include<queue>

#include<vector>

#include<iostream>

using namespace std;

#define  N  11000

int n,m,sum;

int indegree[N],value[N];

vector<int>now[N];

int Max(int a,int b) {

return a>b?a:b;

}

int find() {

       queue<int>q;

  int i,cur,f;

  for(i=1;i<=n;i++)

if(indegree[i]==0) {

value[i]=888;

q.push(i);

}

f=n;

while(!q.empty()) {

cur=q.front();

q.pop();

f--;

for(i=0;i<now[cur].size();i++) {

        value[now[cur][i]]=Max(value[cur]+1,value[now[cur][i]]);

if(--indegree[now[cur][i]]==0)

q.push(now[cur][i]);

}

}

if(f==0)

return 0;

return 1;

}

int main() {

int i,a,b;

while(scanf("%d%d",&n,&m)!=EOF) {

for(i=1;i<=n;i++)

now[i].clear();

memset(indegree,0,sizeof(indegree));

memset(value,0,sizeof(value));

while(m--) {

scanf("%d%d",&a,&b);

    indegree[a]++;

now[b].push_back(a);

}

if(find()) {

printf("-1\n");

continue;

}

sum=0;

for(i=1;i<=n;i++)

sum+=value[i];

printf("%d\n",sum);

}

return 0;

}