19.2.12 [LeetCode 69] Sqrt(x)

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) {
        int s = 0, e = sqrt(INT_MAX);
        while (s <= e) {
            int mid = (s + e) / 2;
            if (mid*mid <= x) 
                s = mid + 1;
            else 
                e = mid - 1;
        }
        return e;
    }
};