Preface: The first topological sorting problem. . .
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:
No two balls share the same label. 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
The problem requires that the larger the number and the heavier the weight, then the reverse construction of the edge, the use of topological sorting, starting from the search with the largest number, when the point with the entry degree of 0 is found, assign a value to this point, and then break, if there is no entry The point with a degree of 0 indicates that there is a ring, then the problem is not met, and -1 is output.
Code
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<queue>
#include<map>
#include<stack>
using namespace std;
typedef long long ll;
const int MAXN=1e4+5;
const int mod=1e9+7;
const int INF =0x3f3f3f;
int e[205][205];
int ans[205];
int in[205];
int n,m;
int toposort()
{
int w,i;
for( w=n;w>=1;w--)
{
for( i=n;i>=1;i--)
{
if(in[i]==0)
{
in[i]--;
ans[i]=w;
for(int j=1;j<=n;j++)
{
if(e[i][j]==1) in[j]--;
}
break;
}
}
if(i==0) break;
}
if(w!=0) return -1;
else return 1;
}
int main()
{
int t;
cin>>t;
while(t--)
{
memset(e,0,sizeof e);
cin>>n>>m;
for(int i=1;i<=n;i++)
{
in[i]=0;
ans[i]=0;
}
int a,b;
for(int i=1;i<=m;i++)
{
cin>>a>>b;
if(e[b][a]==0)
{
e[b][a]=1;
in[a]++;
}
}
if(toposort()==1)
{
for(int i=1;i<=n;i++)
{
cout<<ans[i]<<" ";
}
cout<<endl;
}
else
{
cout<<-1<<endl;
}
}
}