HNU 12886 Cracking the Safe 二十四点的判断

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cstdlib>
 5 #include <cmath>
 6 #include <algorithm>
 7 #include <string>
 8 #include <queue>
 9 #include <stack>
10 #include <vector>
11 #include <map>
12 #include <set>
13 #include <functional>
14 #include <time.h>
15 
16 using namespace std;
17 
18 const int INF = 1<<30;
19 const double eps = 1e-6;
20 
21 double a[4];
22 inline double myAbs(double x) {
23     return x>0 ? x : -x;
24 }
25 
26 bool dfs(double S[], int cnt) { //S[]中存放当前还有的数字
27 //计算方法： 每次从剩下的数字里取出两个数运算，相当于枚举运算顺序
28     if (cnt==1) //最后一个数字
29         return myAbs(24-S[0])<eps;
30 
31     double b[4];
32     for (int i = 0; i < cnt; i++) //枚举两个运算的数字
33         for (int j = 0; j < cnt; j++) if (i!=j) {
34             for (int k = 0, p = 1; k < cnt; k++) {
35                 if (k!=i&&k!=j)
36                     b[p++] = S[k];
37             }
38             //枚举运算
39             b[0] = S[i]+S[j];
40             if (dfs(b, cnt-1)) return true;
41             b[0] = S[i]-S[j];
42             if (dfs(b, cnt-1)) return true;
43             b[0] = S[i]*S[j];
44             if (dfs(b, cnt-1)) return true;
45             b[0] = S[i]/S[j];
46             if (dfs(b, cnt-1)) return true;
47         }
48     return false;
49 }
50 
51 void solve() {
52     do { //枚举排列
53         if (dfs(a, 4)) {
54             puts("YES");
55             return ;
56         }
57     }while (next_permutation(a, a+4));
58     puts("NO");
59 }
60 
61 int main() {
62     #ifdef Phantom01
63         freopen("HNU12879.txt", "r", stdin);
64     #endif //Phantom01
65 
66     int T;
67     scanf("%d", &T);
68     while (T--) {
69         for (int i = 0; i < 4; i++)
70             scanf("%lf", &a[i]);
71         solve();
72     }
73 
74     return 0;
75 }