leetcode 679. 24 点游戏

 1 class Solution {
 2 public:
 3     const double eps=1e-6;
 4     int isok(vector<int>& cards)
 5     {
 6         vector<double>dp[4][4];
 7         for(int i=0;i<4;i++)dp[i][i].push_back((double)cards[i]);
 8         for(int len=2;len<=4;len++)
 9         for(int i=0;i+len-1<4;i++)
10         {
11             int j=i+len-1;
12             for(int k=i;k)
13             {
14                 int n1=dp[i][k].size(),n2=dp[k+1][j].size();
15                 for(int ii=0;ii)
16                 for(int jj=0;jj)
17                 {
18 
19                     dp[i][j].push_back(dp[i][k][ii]+dp[k+1][j][jj]);
20                     dp[i][j].push_back(dp[i][k][ii]-dp[k+1][j][jj]);
21                     dp[i][j].push_back(dp[i][k][ii]*dp[k+1][j][jj]);
22                     if(dp[k+1][j][jj])dp[i][j].push_back(dp[i][k][ii]/dp[k+1][j][jj]);
23                 }
24             }
25         }
26         for(auto &p:dp[0][3]) if(abs(p-24)return true; 
27         return false;
28     }
29     bool judgePoint24(vector<int>& cards) {
30         sort(cards.begin(),cards.end());
31         int n=24;
32         
33         while(n)
34         {
35             if(isok(cards))return true;
36             next_permutation(cards.begin(),cards.end());
37             n--;
38         }
39         return false;
40     }
41 };