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 = 5;
vector<int> trace;
vector<bool> visit(N);
int graph[N][N] = {{1, 1, 0, 0, 0},
                   {0, 0, 1, 0, 0},
                   {0, 0, 0, 1, 1},
                   {0, 1, 0, 0, 1},
                   {1, 0, 0, 0, 0}};

void cycle(int v) {
    if (visit[v]) {
        int beg = 0;
        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 = 0; i < N; i++) {
        if (graph[v][i]) cycle(i);
    }
    trace.pop_back();
    visit[v] = false;
}

int main() {
    cycle(0);
    return 0;
}