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
}
​