leetcode464 Can I Win

思路：

博弈。

实现：

 class Solution
 {
 public:
     bool dfs(int cur, int len, int sum, int des, vector<int>& dp)
     {
         if (sum >= des) return false;
         if (dp[cur] != -) return dp[cur];
         for (int i = ; i < len; i++)
         {
             int tmp =  << i;
             if (!(cur & tmp))
             {
                 if (!dfs(cur | tmp, len, sum + i + , des, dp))
                     return dp[cur] = true;
             }
         }
         return dp[cur] = false;
     }
     bool canIWin(int maxChoosableInteger, int desiredTotal)
     {
         if (!desiredTotal) return true;
         if ((maxChoosableInteger * (maxChoosableInteger + ) / ) < desiredTotal)
             return false;
         vector<int> dp(, -);
         return dfs(, maxChoosableInteger, , desiredTotal, dp);
     }
 };