Codeforces Round #351 (VK Cup 2016 Round 3, Div. 2 Edition) D Bear and Two Paths

题目链接：

http://codeforces.com/contest/673/problem/D

题意：

给四个不同点a,b,c,d，求是否能构造出两条哈密顿通路，一条a到b，一条c到d。

题解：

构造法，看例子：

input：

5 6

5 2 4 1

output:

5 4 3 1 2

4 5 3 2 1

所以只要满足k>=n+1,就可以构造出来答案。

#include<iostream>
#include<cstring>
#include<cstdio>
#include<vector>
#include<queue>
using namespace std;

int n, m;

const int maxn = 1111;
int arr[maxn],mp[maxn];
int arr2[maxn];

int main() {
    int a, b, c, d;
    while (scanf("%d%d", &n, &m) == 2 && n) {
        scanf("%d%d%d%d", &a, &b, &c, &d);
        if (n ==4 || m < n + 1) {
            printf("-1
"); continue;
        }
        memset(mp, 0, sizeof(mp));
        memset(arr, 0, sizeof(arr));
        mp[a] = mp[b] = mp[c] = mp[d] = 1;
        arr[1] = a; arr[n] = b;
        arr[2] = c; arr[4] = d;
        int tot = 5;
        for (int i = 1; i <= n; i++) {
            if (mp[i]) continue;
            if (arr[3] == 0) arr[3] = i;
            else {
                arr[tot++]= i;
            }
        }
        for (int i = 1; i < n; i++) printf("%d ", arr[i]); printf("%d
", arr[n]);

        memset(arr2, 0, sizeof(arr2));
        arr2[1] = c; arr2[n] = d; arr2[2] = arr[1]; arr2[3] = arr[3];
        tot = 4;
        for (int i = n; i >=5; i--) arr2[tot++] = arr[i];
        for (int i = 1; i < n; i++) printf("%d ", arr2[i]); printf("%d
", arr2[n]);
    }
    return 0;
}