One algorithm a day: floor of the square root of the input

Description

Implement a function that takes in a 32 bit integer and returns another 32 bit unsigned integer that is the floor of the square root of the input

Implementation

Function can be implemented in easy way using binary search. We will start evaluating numbers from middle and move left or right depending if the center element is bigger or smaller. Here is sample solution implemented in Swift:

func root(_ input:Int32 )->Int32?{
    //Base case
    if(input == 0){return 0}
    if(input == 1){return 1}


    var left:Int32 = 0
    var right = input
    var middle = (right + left) / 2
    
    while left < right {
        
        let tempResult = middle * middle
        //left middle right
        if tempResult == input{ // Voila. Root found
            return middle
        }
        else if tempResult > input{ // Too big
            right = middle - 1
        }
        else{//too small
            left = middle + 1
        }
            middle = (right + middle) / 2
    }
    
    
    return nil
}

//Testing
root(4) // 2
root(2)
root(9)