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:

Binary Search. The square root of x is within [0…(x+1)/2].

/**
 * @param {number} x
 * @return {number}
 */
var mySqrt = function(x) {
  let max = Math.round(x / 2)
  let min = 0
  while (min <= max) {
    const mid = Math.floor((min + max) / 2)
    const diff = mid * mid - x
    if (diff > 0) {
      max = mid - 1
    } else if (diff < 0) {
      min = mid + 1
    } else {
      return mid
    }
  }
  return max
};

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