【ccf- csp201509-4】高速公路

 #include<iostream>
 using namespace std;
 void DFS(int**mat, int *mark,int *sp, int n, int p)
 {
     int i;
     //DFS每个顶点
     if(!mark[p])
     for(i=;i<=n;i++)
         if (mat[p][i]&&i!=p)//<p,i>
         {
             mark[p] = ;
             sp[p] = ;
             DFS(mat,mark,sp, n, i);
             mark[p] = ;
         }
 }
 int main()
 {
     int n, m,i,j; cin >> n >> m;
     int**mat = new int*[n+];
     for (i = ; i <= n; i++)
         mat[i] = new int[n+];
     for (i = ; i <= n; i++)
         for (j = ; j <= n; j++)
             mat[i][j] = ;
     int a, b;
     for (i = ; i < m; i++)
     {
         cin >> a >> b;
         mat[a][b] = ;
     }
     int *mark = new int[n + ];
     int *sp = new int[n + ];
     int sum = ,k;
     for (i = ; i <= n; i++)
         mark[i] = ;
     for (i = ; i < n; i++)
     {
         for (k = ; k <= n; k++)
             sp[k] = ;
         DFS(mat, mark, sp, n, i);
         for (j = i + ; j <= n; j++)
         {
             if (sp[j])//<i,j>
             {
                 for (k = ; k <= n; k++)
                     sp[k] = ;
                 DFS(mat, mark, sp, n, j);
                 if (sp[i])//<j,i>
                     sum++;
             }
         }
     }
     cout << sum << endl;
     return ;
 }