hdu 1342 and poj 2245 Lotto,dfs
Lotto
Problem Description
In a Lotto I have ever played, one has 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 file 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
#include <iostream> #include <cstdio> using namespace std; int k, a[13], ans[6]; void dfs(int cur, int st) { if(cur == 6) { printf("%d", a[ans[0]]); for(int i = 1; i <6; i++) printf(" %d", a[ans[i]]); printf("\n"); return; } for(int i = st+1; i < k; i++) { ans[cur] = i; dfs(cur+1, i); } } int main() { bool flag = false; while(scanf("%d", &k), k) { for(int i = 0; i < k; i++) scanf("%d", &a[i]); if(flag) printf("\n"); flag = true; for(int i = 0; i <= k-6; i++) { ans[0] = i; dfs(1, i); } } return 0; }
在网上看到一种更神的方法,真乃业界神人:
#include <iostream> #include <cstdio> using namespace std; int main() { int k, a[14]; bool flag = false; while(scanf("%d", &k), k) { for(int i = 0; i < k; i++) scanf("%d", &a[i]); if(flag) printf("\n"); flag = true; for(int i = 0; i < k-5; i++) for(int j = i+1; j < k-4; j++) for(int l = j+1; l < k-3; l++) for(int m = l+1; m < k-2; m++) for(int n = m+1; n < k-1; n++) for(int p = n+1; p < k; p++) printf("%d %d %d %d %d %d\n", a[i], a[j], a[l], a[m], a[n], a[p]); } return 0; }