HDOJ Lotto (DFS)

Lotto

Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 131072/65536K (Java/Other)

Total Submission(s) : 15   Accepted Submission(s) : 7

Problem Description

In the German Lotto you have to select 6 numbers from the set {1,2,...,49}. A popular strategy to play Lotto - although it doesn't increase your chance of winning - is to select a subset S containing k (k > 6) of these 49 numbers, and then play several games with choosing numbers only from S. For example, for k=8 and S = {1,2,3,5,8,13,21,34} there are 28 possible games: [1,2,3,5,8,13], [1,2,3,5,8,21], [1,2,3,5,8,34], [1,2,3,5,13,21], ... [3,5,8,13,21,34].

Your job is to write a program that reads in the number k and the set S and then prints all possible games choosing numbers only from S.

 

Input

The input will contain one or more test cases. Each test case consists of one line containing several integers separated from each other by spaces. The first integer on the line will be the number k (6 < k < 13). Then k integers, specifying the set S, will follow in ascending order. Input will be terminated by a value of zero (0) for k.

 

Output

For each test case, print all possible games, each game on one line. The numbers of each game have to be sorted in ascending order and separated from each other by exactly one space. The games themselves have to be sorted lexicographically, that means sorted by the lowest number first, then by the second lowest and so on, as demonstrated in the sample output below. The test cases have to be separated from each other by exactly one blank line. Do not put a blank line after the last test case.

 

Sample Input

7 1 2 3 4 5 6 78 1 2 3 5 8 13 21 340

 

Sample Output

1 2 3 4 5 61 2 3 4 5 71 2 3 4 6 71 2 3 5 6 71 2 4 5 6 71 3 4 5 6 72 3 4 5 6 71 2 3 5 8 131 2 3 5 8 211 2 3 5 8 341 2 3 5 13 211 2 3 5 13 341 2 3 5 21 341 2 3 8 13 211 2 3 8 13 341 2 3 8 21 341 2 3 13 21 341 2 5 8 13 211 2 5 8 13 341 2 5 8 21 341 2 5 13 21 341 2 8 13 21 341 3 5 8 13 211 3 5 8 13 341 3 5 8 21 341 3 5 13 21 341 3 8 13 21 341 5 8 13 21 342 3 5 8 13 212 3 5 8 13 342 3 5 8 21 342 3 5 13 21 342 3 8 13 21 342 5 8 13 21 343 5 8 13 21 34这道题第一眼我以为是全排列，但是看了一下样例(英文看不懂)(逃，怎么能有这么少呢，原来这些排列都是单调递增的 ,和全排列一样，只是保证下次取得数比前一次的大，所以我们就可以对输入的数字排序一下ac代码：
#include<stdio.h>#include<string.h>#include<iostream>#include<algorithm>#define MAXN 110using namespace std;int num[MAXN];int v[MAXN];int a[7];int n,cas;void dfs(int x,int low){if(x==7){for(int i=1;i<6;i++)printf("%d ",a[i]);printf("%d\n",a[6]);return;}for(int i=low;i<n;i++){if(v[i]==0){a[x]=num[i];v[i]=1;dfs(x+1,i);//因为排序后数组就递增了，所以，直接取当前数字为下界v[i]=0;}}}int main(){int i;while(scanf("%d",&n)!=EOF,n){memset(v,0,sizeof(v));if(cas)//这是个坑printf("\n");for(i=0;i<n;i++)scanf("%d",&num[i]);sort(num,num+n);dfs(1,0);cas++;}return 0;}