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.
class Solution {
    public int mySqrt(int x) {
        if(x == 0) return 0;
        
        int left = 1, right = x;
        while(left != right) {
            int mid = left + ((right - left) / 2);
            if (x / mid >= mid && x / (mid + 1) < (mid + 1)) {
                return mid;
            } else if (x / mid >= mid && x / (mid + 1) >= (mid + 1)) {
                left = mid == left ? mid + 1 : mid;
            } else {
                right = mid;
            }
        }
        return left;
    }
}
class Solution {
    private int binarySearch(long low, long high, int x) {        
        if (low == high)
            return (int)low;
        long mid = (high + low) / 2;
        if ((mid * mid == x) || (low == mid))
            return (int)mid;
        else if (mid * mid > x)
            return binarySearch(low, mid, x);
        else
            return binarySearch(mid, high, x);
    }
    
    public int mySqrt(int x) {
        if (x == 0)
            return 0;
        return binarySearch(1, x, x);
    }
}