69. Sqrt(x)

題目原文

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.

解題思路

程式解答

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