mySqrt.js

/*
69. Sqrt(x)
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.
*/

var mySqrt = function(x) {
    // for(let i = 0; i <= x + 1; i++){
    //     if(i*i > x) {
    //         return i - 1;
    //     }
    // }

    //  Binary Search Solution
    if (x < 2) return x;
    let left = 1;
    let right = Math.floor(x / 2);
    
    while (left <= right) {
        let mid = Math.floor((left + right) / 2);
        
        if (mid * mid === x) {
            return mid
        } else if (mid * mid > x) {
            right = mid - 1;
        } else {
            left = mid + 1;
        }
    }
    return right;
};

console.log(mySqrt(4))