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lc367 有效完全平方数

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`@@ -112,6 +112,29 @@ class Solution:`
`112`	`112`
`113`	`113`	```
`114`	`114`
	`115`	`+### [有效的完全平方数](https://leetcode.cn/problems/valid-perfect-square/)`
	`116`	`+> 给定一个正整数 num ,编写一个函数,如果 num 是一个完全平方数,则返回 true ,否则返回 false 。`
	`117`	`+> 进阶:不要使用任何内置的库函数,如 sqrt 。`
	`118`	`+`
	`119`	+思路:只要`num`大于4,其平方数肯定不会超过`num//2`,这样可以减少一次二分运算,提升速度.
	`120`	`+`
	`121`	`+Python版本`
	`122`	+```python
	`123`	`+class Solution:`
	`124`	`+ def isPerfectSquare(self, num: int) -> bool:`
	`125`	`+ left, right = 1, num // 2 + 1`
	`126`	`+ while left + 1 < right:`
	`127`	`+ mid = left + (right - left) // 2`
	`128`	`+ if mid * mid == num: return True`
	`129`	`+ elif mid * mid < num: left = mid`
	`130`	`+ else:`
	`131`	`+ right = mid`
	`132`	`+ if left * left == num or right * right == num: return True`
	`133`	`+ else: return False`
	`134`	+```
	`135`	`+`
	`136`	`+`
	`137`	`+`
`115`	`138`	`### [猜数字大小](https://leetcode.cn/problems/guess-number-higher-or-lower/)`
`116`	`139`	`> 猜数字游戏的规则如下:`
`117`	`140`	`> 每轮游戏,我都会从 1 到 n 随机选择一个数字。请你猜选出的是哪个数字。`

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