69 - Sqrt(x)

#easy

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.

class Solution {
public:
    int mySqrt(int x) {
        if ( x == 0 ) return 0;
        if ( x == 1 ) return 1;
        double left = 0, right = x;
        double mid = 0;
        while ( (int) right - (int) left != 0 ) {
            mid = ( left + right ) / 2;
            if ( mid * mid > x ) right = mid;
            else if ( mid * mid < x ) left = mid;
            else return mid;
        }

        return (int) mid;
    }
};