69. Sqrt(x)

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.

/**
 * @param {number} x
 * @return {number}
 */
var mySqrt = function(x) {
    if (x < 0) {
        return NaN;
    }
    if (x <=1 ) {
        return x;
    }
    let val = x;
    let last;
    do {
        last = val;
        val = (val + x / val) / 2;
    }
    while (Math.abs(val - last) >= 1);
    return Math.floor(val);
};