poj2367 Genealogical tree

思路：

拓扑排序，这里是用染色的dfs实现的。在有环的情况下可以判断出来，没有环的情况下输出拓扑排序序列。

实现：

 #include <vector>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 #define w 0
 #define g 1
 #define b 2
 using namespace std;
 const int N = ;
 int G[N][N];
 vector<int> res, vis;
 bool cycle;
 int n, m;
 void init()
 {
     cycle = false;
     cin >> n;
     memset(G, , sizeof G);
     for (int i = ; i <= n; i++) vis.push_back(w);
     int x;
     for (int i = ; i <= n; i++)
     {
         while (cin >> x, x)
         {
             G[i][x] = ;
         }
     }
 }
 void dfs(int u)
 {
     if (vis[u] == b) return;
     if (vis[u] == g) { cycle = true; return; }
     vis[u] = g;
     for (int i = n; i >= ; i--)
     {
         if (G[u][i]) dfs(i);
     }
     vis[u] = b;
     res.push_back(u);
     return;
 }
 void topsort()
 {
     for (int i = n; i >= ; i--)
     {
         if (vis[i] == w) dfs(i);
     }
     reverse(res.begin(), res.end());
 }
 int main()
 {
     init();
     topsort();
     if (cycle) cout << "There is a cycle in G!" << endl;
     else
     {
         for (int i = ; i < res.size(); i++)
             cout << res[i] << " ";
         cout << endl;
     }
     return ;
 }