leetcode 69. Sqrt(x)

Seawolf

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) {
        long start = 0;
        long mid = 0;
        long end = x;
        
        while(start+ 1 < end){
            
            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;
        
        return (int)start;
    }
}