leedcode x的平方根

暴力搜索

class Solution:
    def mySqrt(self, x: int) -> int:
        if x>=100 and x<10000:
            i=10
        elif x>=10000 and x<1000000:
            i=100
        elif x>=1000000:
            i=1000
        else:
            i=0



        flag=True
        while flag:
            if i*i==x:

                return i
            elif i*i<x and (i+1)*(i+1)>x:

                return i
            else:
                i+=1

二分法

class Solution:
    def mySqrt(self, x: int) -> int:
        if x == 0:
            return 0
        left = 1
        right = x
        res = 0
        while left <= right:
            mid = left + (right - left) // 2
            if mid*mid== x:
                return mid
            elif mid * mid < x:
                left = mid + 1
                res = mid
            else:
                right = mid - 1
        return res