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LeetCode 69. Sqrt(x) (javascript solution)

cod3pineapple profile image codingpineapple ・1 min read


Given a non-negative integer x, compute and return the square root of x.

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


Time Complexity : O(log(n))
Space Complexity: O(1)

// Binary search approach
var mySqrt = function(x) {
    let left = 1;
    let right = x;
    // The square root of 0 or 1 is itself
    if(x < 2) return x;

    // Use binary search to find the square root or the whole number closest to the square root
    while(left < right) {
        // Find the mid point between left and right
        const mid = Math.floor((left + right) / 2)
        // Return the mid point if this is the square root
        if(mid*mid === x) return mid
        // If mid squared is greater than x then the answer must be on the left half of mid
        else if(mid*mid >x) right = mid
        // If mid squred is less than x then the answer must be on the right half of mid
        else left = mid+1
    return left - 1
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