HDU2647 拓扑排序

#include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
#include <cmath>
#include <string>
#include <string.h>
#include <algorithm>
using namespace std;
#define LL __int64
#define eps 1e-8
#define INF 1e8
#define lson l , m , rt << 1
#define rson m + 1 , r , rt << 1 | 1
const int MOD = 2333333; 
const int maxn = 10000 + 5;
int Rank[maxn] , degree[maxn];
vector <int> graph[maxn];
int n , m;

bool toposort()
{
    int i , j , u , v , tot;
    tot = 0;
    memset(Rank , 0 , sizeof(Rank));
    memset(degree , 0 , sizeof(degree));
    for(int i = 1 ; i <= n ; i++)
        for(int j = 0 ; j < graph[i].size() ; j++)
            degree[ graph[i][j] ] ++;
    queue <int> que;
    for(int i = 1 ; i <= n ; i++) {
        if(degree[i] == 0) {
            que.push(i);
            Rank[i] = 0;
            tot++;
        }
    }
    while(!que.empty()) {
        int u = que.front();
        que.pop();
        for(int i = 0 ; i < graph[u].size() ; i++) {
            int tmp = graph[u][i];
            degree[tmp]--;
            if(degree[tmp] == 0) {
                que.push(tmp);
                Rank[tmp] = Rank[u] + 1;    //就是这里，工资要多1
                tot++;
            }
        }
    }
    return tot == n;
}
int main()
{
    int a , b;
    while(~scanf("%d %d" , &n , &m))
    {
        for(int i = 1 ; i <= n ; i++)
            graph[i].clear();
        while(m--) {
            scanf("%d %d" , &a , &b);
            graph[b].push_back(a);        
        }
        if(toposort()) {
            int res = 888 * n;
            for(int i = 1 ; i <= n ; i++)
                res += Rank[i];
            printf("%d\n" , res);
        } else {
            printf("-1\n");
        }
    }
    return 0;
}