Labeling Balls--poj3687

Labeling Balls

Description

Windy has N balls of distinct weights from 1 unit to N units. Now he tries to label them with 1 to N in such a way that:

1. No two balls share the same label.
2. The labeling satisfies several constrains like "The ball labeled with a is lighter than the one labeled with b".

Can you help windy to find a solution?

Input

The first line of input is the number of test case. The first line of each test case contains two integers, N (1 ≤ N ≤ 200) and M (0 ≤ M ≤ 40,000). The next M line each contain two integers a and b indicating the ball labeled with a must be lighter than the one labeled with b. (1 ≤ a, b ≤ N) There is a blank line before each test case.

Output

For each test case output on a single line the balls‘ weights from label 1 to label N. If several solutions exist, you should output the one with the smallest weight for label 1, then with the smallest weight for label 2, then with the smallest weight for label 3 and so on... If no solution exists, output -1 instead.

Sample Input

5

4 0

4 1
1 1

4 2
1 2
2 1

4 1
2 1

4 1
3 2

Sample Output

1 2 3 4
-1
-1
2 1 3 4
1 3 2 4

这是一个拓扑题，还不是普通的拓扑，这必须要反向建图+逆向输出，并且注意，这个题让输出的是各个人的位置！！！

 1 #include <iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4
 5 using namespace std;
 6 int map[250][250];
 7 int degree[250];
 8 void topo(int n)
 9 {
10     int i,j,mark,que[250];
11     for(i=n;i>=0;i--)
12     {
13         int x=0;//标记看是否满足要求
14         for(j=n;j>=0;j--)
15         {
16             if(degree[j]==0)
17             {
18                 x=1;
19                 mark=j;
20                 break;
21             }
22         }
23         if(x==0)
24             break;
25         que[mark]=i;
26         degree[mark]=-1;
27         for(j=1;j<=n;j++)
28         {
29             if(map[mark][j])
30                 degree[j]--;
31         }
32     }
33     if(i!=-1)
34         printf("-1\n");
35     else
36     {
37         printf("%d",que[1]);
38         for(i=2;i<=n;i++)
39         printf(" %d",que[i]);
40         printf("\n");
41
42     }
43 }
44
45 int main()
46 {
47     int N,i,m,n,a,b;
48     scanf("%d",&N);
49     while(N--)
50     {
51         memset(map,0,sizeof(map));
52         memset(degree,0,sizeof(degree));
53         scanf("%d%d",&n,&m);
54         for(i=0;i<m;i++)
55         {
56             scanf("%d%d",&a,&b);
57             if(!map[b][a])//避免重复录入
58             {
59                 map[b][a]=1;
60                 degree[a]++;//反向建图
61             }
62         }
63         topo(n);
64     }
65     return 0;
66 }