69. Sqrt(x)

https://leetcode.com/problems/sqrtx/

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.

Solution

class Solution {
public:
    int mySqrt(int x) {
        if (x == 0) return 0;
        int begin = 1, end = x;
        while (begin < end) {
            int mid = begin + (end - begin + 1) / 2;
            if (mid <= x / mid) {
                begin = mid;
            } else {
                end = mid - 1;
            }
        }
        return begin;
    }
};

• #binarysearch