http://acm.hdu.edu.cn/showproblem.php?pid=1427
简单的dfs枚举所有情况就行
符号的组合实际上有两种
((ab)c)d 和 (ab)(cb)
dfs(sum+pos, cur+1, num[cur+1]); dfs(sum-pos, cur+1, num[cur+1]); dfs(sum*pos, cur+1, num[cur+1]); if(pos != 0 && sum%pos == 0) dfs(sum/pos, cur+1, num[cur+1]); dfs(sum, cur+1, pos+num[cur+1]); dfs(sum, cur+1, pos-num[cur+1]); dfs(sum, cur+1, pos*num[cur+1]); if(num[cur+1] != 0 && pos%num[cur+1] == 0) dfs(sum, cur+1, pos/num[cur+1]);
#include <iostream> #include <fstream> #include <cstring> #include <algorithm> using namespace std; int num[4]; bool flag = 0; void dfs(int sum, int cur, int pos) { if(flag) return; if(cur == 3) { if(sum + pos == 24) flag = 1; if(sum - pos == 24) flag = 1; if(sum * pos == 24) flag = 1; if(pos != 0 && sum%pos == 0 && sum/pos == 24) flag = 1; return; }dfs(sum+pos, cur+1, num[cur+1]); dfs(sum-pos, cur+1, num[cur+1]); dfs(sum*pos, cur+1, num[cur+1]); if(pos != 0 && sum%pos == 0) dfs(sum/pos, cur+1, num[cur+1]); dfs(sum, cur+1, pos+num[cur+1]); dfs(sum, cur+1, pos-num[cur+1]); dfs(sum, cur+1, pos*num[cur+1]); if(num[cur+1] != 0 && pos%num[cur+1] == 0) dfs(sum, cur+1, pos/num[cur+1]);}int main(void){// freopen("1.txt", "r", stdin); char str[100]; while(cin>>str) { if(str[0] == 'A') num[0] = 1; else if(str[0] == 'J') num[0] = 11; else if(str[0] == 'Q') num[0] = 12; else if(str[0] == 'K') num[0] = 13; else if(str[0] == '1' && str[1] == '0') num[0] = 10; else num[0] = str[0] - '0'; for(int i = 1; i < 4; i ++) { cin>>str; if(str[0] == 'A') num[i] = 1; else if(str[0] == 'J') num[i] = 11; else if(str[0] == 'Q') num[i] = 12; else if(str[0] == 'K') num[i] = 13; else if(str[0] == '1' && str[1] == '0') num[i] = 10; else num[i] = str[0] - '0'; } sort(num, num+4); flag = 0; do { dfs(num[0], 1, num[1]); } while(next_permutation(num, num+4)&&!flag); if(flag) cout<<"Yes"<<endl; else cout<<"No"<<endl; } return 0;}