[Swift]LeetCode375. 猜数字大小 II | Guess Number Higher or Lower II
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➤微信公众号:山青咏芝(shanqingyongzhi)
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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.
我们正在玩一个猜数游戏,游戏规则如下:
我从 1 到 n 之间选择一个数字,你来猜我选了哪个数字。
每次你猜错了,我都会告诉你,我选的数字比你的大了或者小了。
然而,当你猜了数字 x 并且猜错了的时候,你需要支付金额为 x 的现金。直到你猜到我选的数字,你才算赢得了这个游戏。
示例:
n = 10, 我选择了8. 第一轮: 你猜我选择的数字是5,我会告诉你,我的数字更大一些,然后你需要支付5块。 第二轮: 你猜是7,我告诉你,我的数字更大一些,你支付7块。 第三轮: 你猜是9,我告诉你,我的数字更小一些,你支付9块。 游戏结束。8 就是我选的数字。 你最终要支付 5 + 7 + 9 = 21 块钱。
给定 n ≥ 1,计算你至少需要拥有多少现金才能确保你能赢得这个游戏。
232ms
1 class Solution { 2 func getMoneyAmount(_ n: Int) -> Int { 3 var memo:[[Int]] = [[Int]](repeating:[Int](repeating:0,count:n + 1),count:n + 1) 4 return helper(1, n, &memo) 5 } 6 7 func helper(_ start:Int,_ end:Int,_ memo:inout [[Int]]) -> Int 8 { 9 if start >= end {return 0} 10 if memo[start][end] > 0 {return memo[start][end]} 11 var res:Int = Int.max 12 for k in start...end 13 { 14 var t:Int = k + max(helper(start, k - 1, &memo), helper(k + 1, end, &memo)) 15 res = min(res, t) 16 } 17 memo[start][end] = res 18 return res 19 } 20 }