HDU-2181 哈密顿绕行世界问题

直接DFS，不用加剪枝。

#include <cstdio>
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <queue>

#define rep(i, l, r) for(int i=l; i<=r; i++)
#define down(i, l, r) for(int i=l; i>=r; i--)
#define maxn 5678
#define MAX 1<<30

using namespace std;

int m, e[21][4], st[21], n, t;
bool b[21]; 

void Search(int x, int n)
{
    if (n == 21) 
    {
        printf("%d:  ", ++t); rep(i, 1, 20) printf("%d ", st[i]); printf("%d
", m); return; 
    }
    if (n == 20)
    {
        st[n] = x; rep(i, 1, 3) if (e[x][i] == m) Search(m, n+1); return;
    }
    b[x] = true; st[n] = x;
    rep(i, 1, 3) if (!b[e[x][i]]) Search(e[x][i], n+1);
    b[x] = false;
}

int main()
{
    rep(i, 1, 20) scanf("%d%d%d", &e[i][1], &e[i][2], &e[i][3]); 
    rep(i, 1, 20) sort(e[i]+1, e[i]+4);
    scanf("%d", &m); while (m) { t = 0; Search(m, 1); scanf("%d", &m); }
    return 0;
}