69. Sqrt(x)

Easy

Given a non-negative integer x, return the square root of x rounded down to the nearest integer. The returned integer should be non-negative as well.

You must not use any built-in exponent function or operator.

• For example, do not use pow(x, 0.5) in c++ or x ** 0.5 in python.

Example 1:

Input: x = 4
Output:
 2
Explanation:
 The square root of 4 is 2, so we return 2.

Example 2:

Input: x = 8
Output:
 2
Explanation:
 The square root of 8 is 2.82842..., and since we round it down to the nearest integer, 2 is returned.

Constraints:

• 0 <= x <= 231 - 1

解題

Binary Search

func mySqrt(x int) int {
    if x == 1 {return 1}
    
    left := 0
    right := x 


    for left < right {
        mid := (right - left + 1) / 2 + left

        product := mid*mid
        if product == x { return mid }

       if product > x {
            right = mid - 1
        } else {
            left = mid 
        }
    }

    return left
}