69. Sqrt(x)

Problem

Implement int sqrt(int x).

Compute and return the square root of x, where x is guaranteed to be a non-negative integer.

Since the return type is an integer, the decimal digits are truncated and only the integer part of the result is returned.

Example 1:

Input: 4
Output: 2

Example 2:

Input: 8
Output: 2
Explanation: The square root of 8 is 2.82842..., and since 
             the decimal part is truncated, 2 is returned.

Solution

/**
 * @param {number} x
 * @return {number}
 */
var mySqrt = function(x) {
  if (x < 2) return x;
  var left = 1;
  var right = x;
  var mid = 0;
  while (left <= right) {
    mid = left + Math.floor((right - left) / 2);
    if (mid > x / mid) {
      right = mid - 1;
    } else if ((mid + 1) > x / (mid + 1)) {
      return mid;
    } else {
      left = mid + 1;
    }
  }
};

Explain:

nope.

Complexity:

• Time complexity : O(log(n)).
• Space complexity : O(1).