Sqrt(x)

Method 1:
Binary Search

Code:

public class Solution {
    public int mySqrt(int x) {
        if (x < 0) return -1;
        if (x == 0) return 0;
        
        long low = 1;
        long high = x/2+1;
        
        while (low <= high){
            long mid = (low+high)/2;
            if (mid * mid == x) return (int) mid;
            else if (mid * mid < x){
                low = mid + 1;
            }else{
                high = mid -1;
            }
        }
    
        return (int)high;
        
    }
}

Another Method:

Newton method.