hdu 2647

来源：互联网发布：优化设计英文编辑：程序博客网时间：2024/04/29 03:22
http://acm.hdu.edu.cn/showproblem.php?pid=2647
#include <iostream>#include <cstdio>#include <queue>#include <cstring>#define MM 10005using namespace std;int inde[MM];int add[MM];  //每人要加的。struct Node{    int data;    Node *next;    Node():data(0),next(0){}}*e[MM];void addEdage(int u,int v){    Node *t =new Node;    t->data=v;    t->next=e[u];    e[u]=t;}void init(int n){    memset(e,0,sizeof(e));    memset(inde,0,sizeof(inde));    int i;    for(i=0;i<=n;i++)        add[i]=888;}int main(){    int n,m;    while(scanf("%d%d",&n,&m)!=EOF)    {        int i,a,b;        init(n);        for(i=0;i<m;i++)        {            scanf("%d%d",&a,&b);            addEdage(b,a);       //注意是反向的            inde[a]++;        }        queue<int> q;        for(i=1;i<=n;i++)        {            if(inde[i]==0)            {                q.push(i);            }        }        int sum=0;        int count=0;        while(!q.empty())        {            int t=q.front();            q.pop();            count++;            sum=sum+add[t];            Node *hh;            for(hh=e[t];hh;hh=hh->next)            {                if(--inde[hh->data]==0)                {                    q.push(hh->data);                    add[hh->data]=add[t]+1;  //注意点                }            }        }        if(count!=n)            printf("-1\n");        else            printf("%d\n",sum);    }    return 0;}