1146 Topological Order

This is a problem given in the Graduate Entrance Exam in 2018: Which of the following is NOT a topological order obtained from the given directed graph? Now you are supposed to write a program to test each of the options.

Input Specification:

Each input file contains one test case. For each case, the first line gives two positive integers N (≤ 1,000), the number of vertices in the graph, and M (≤ 10,000), the number of directed edges. Then M lines follow, each gives the start and the end vertices of an edge. The vertices are numbered from 1 to N. After the graph, there is another positive integer K (≤ 100). Then K lines of query follow, each gives a permutation of all the vertices. All the numbers in a line are separated by a space.

Output Specification:

Print in a line all the indices of queries which correspond to “NOT a topological order”. The indices start from zero. All the numbers are separated by a space, and there must no extra space at the beginning or the end of the line. It is graranteed that there is at least one answer.

Sample Input:

6 8
1 2
1 3
5 2
5 4
2 3
2 6
3 4
6 4
5
1 5 2 3 6 4
5 1 2 6 3 4
5 1 2 3 6 4
5 2 1 6 3 4
1 2 3 4 5 6

Sample Output:

3 4

浅析

简单的拓扑排序判断

Code

#include 
#include 
using namespace std;

int main(){
    int n, m;
    cin >> n >> m;
    vector<int> G[n+1];
    vector<int> degree(n+1, 0);
    for (int i = 0;i
        int a1, a2;
        cin >> a1 >> a2;
        G[a1].push_back(a2);
        degree[a2]++;
    }
    int k;
    cin>>k;
    vector <int> result;
    for(int i=0;i
        vector<int> degree_c = degree;
        int flag = true;
        for (int j = 0; j < n; j++){
            int temp;
            cin >> temp;
            if(degree_c[temp]!=0)
                flag = false;
            for (int z = 0; z < G[temp].size();z++)
                degree_c[G[temp][z]]--;
        }
        if(!flag)
            result.push_back(i);
    }
    for (int i = 0; i < result.size();i++){
        printf("%d",result[i]);
        if(i!=result.size()-1)
            printf(" ");
    }
    return 0;
}