LeetCode [375] Guess Number Higher or Lower II

 375. Guess Number Higher or Lower II

Medium

We are playing the Guess Game. The game is as follows:

I pick a number from 1 to n. You have to guess which number I picked.

Every time you guess wrong, I'll tell you whether the number I picked is higher or lower.

However, when you guess a particular number x, and you guess wrong, you pay $x. You win the game when you guess the number I picked.

Example:

n = 10, I pick 8.

First round:  You guess 5, I tell you that it's higher. You pay $5.
Second round: You guess 7, I tell you that it's higher. You pay $7.
Third round:  You guess 9, I tell you that it's lower. You pay $9.

Game over. 8 is the number I picked.

You end up paying $5 + $7 + $9 = $21.

Given a particular n ≥ 1, find out how much money you need to have to guarantee a win.

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class Solution { int[][] dp; public int getMoneyAmount(int n) { dp = new int[n+1][n+1]; return helper(1, n); } int helper(int start, int end){ if(start>=end) return 0; if(dp[start][end]>0) return dp[start][end]; int ret = Integer.MAX_VALUE; for(int i=start; i<=end; ++i){ int r = i + Math.max(helper(start, i-1), helper(i+1, end)); ret = Math.min(ret, r); } dp[start][end] = ret; return ret; } }