69. Sqrt(x)

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Problem

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.

Code

class Solution {
    public int mySqrt(int x) {
        long start = 1;
        long end = x;

        while(start + 1 < end){
            long mid = start + (end - start) / 2;

            if(mid * mid == x){
                return (int)mid;
            } else if (mid * mid < x){
                start = mid;
            } else {
                end = mid;
            }
        }

        if(end * end <= x){
            return (int)end;
        } else {
            return (int)start;
        }
    }
}