uva 10344

题意：给你一些数，问你是否能通过+ ，-， *，让结果等于23，注意的地方是：这些数可以任意排序

#include <iostream>#include <cstring>#include <cstdio>using namespace std;int a[5];int vis[5];int flag;void dfs(int cur,int sum){if (cur == 5 && sum == 23){flag = 1;return;}for (int i = 0 ; i < 5 ; i++){if (!vis[i]){vis[i] = 1;dfs(cur+1,sum+a[i]);dfs(cur+1,sum-a[i]);dfs(cur+1,sum*a[i]);vis[i] = 0 ;}}}int main(){while (1){flag = 0;for (int i = 0 ; i< 5 ; i++)cin>>a[i];for (int i = 0 ; i < 5 ; i++)if (a[i])flag = 1 ;if (!flag)break;flag = 0;for (int i = 0 ; i < 5 ; i++){memset(vis,0,sizeof(vis));vis[i] = 1 ;dfs(1,a[i]);}if (flag)  cout << "Possible" << endl;  else  cout << "Impossible" << endl;}return 0 ;}