【LeetCode】69. Square root of X

1. subject

Do not use system built-in functions , Please give the square root of a number .

2. thought

Use dichotomy .

• Pay attention to the treatment of special values 【 I flipped the car here twice 】

3. Code

class Solution:
    def mySqrt(self, x: int) -> int:
        low,high=0,x
        
        #  Find a suitable subscript , Even if they are equal , Also continue to find 
        while(low <= high):
            mid=(low+high) //2 
            # print(low,high,mid)
            if x == mid * mid:
                return mid
            if mid == 0: #  If mid = 0, So it must be low=0,high = 1
                low = mid+1
                continue
            if x // mid >= mid: #  If 
                low = mid + 1
            else:
                high = mid - 1 
        
        #  end while when , low > high
        #  Finally, let's judge 
        return high