Data Structure Graph: cycle in a directed graph

geeks上的解答复杂了些，用回溯就行了

 #include <iostream>
 #include <vector>
 #include <algorithm>
 #include <queue>
 #include <stack>
 #include <string>
 #include <fstream>
 using namespace std;

 const int N = ;
 vector<int> trace;
 vector<bool> visit(N);
 int graph[N][N] = {{, , , , },
                    {, , , , },
                    {, , , , },
                    {, , , , },
                    {, , , , }};

 void cycle(int v) {
     if (visit[v]) {
         int beg = ;
         for (; beg < trace.size(); ++beg)
             if (trace[beg] == v) break;
         for (int i = beg; i < trace.size(); i++) {
             cout << trace[i] << " ";
         }
         cout << endl;
         return;
     }
     visit[v] = true;
     trace.push_back(v);
     for (int i = ; i < N; i++) {
         if (graph[v][i]) cycle(i);
     }
     trace.pop_back();
     visit[v] = false;
 }

 int main() {
     cycle();
     return ;
 }