69. Sqrt(x)

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Given a non-negative integer x, return the square root of x rounded down to the nearest integer. The returned integer should be non-negative as well.

You must not use any built-in exponent function or operator.

For example, do not use pow(x, 0.5) in c++ or x ** 0.5 in python.
 

Example 1:

Input: x = 4
Output: 2
Explanation: The square root of 4 is 2, so we return 2.
Example 2:

Input: x = 8
Output: 2
Explanation: The square root of 8 is 2.82842..., and since we round it down to the nearest integer, 2 is returned.
 

Constraints:

0 <= x <= 231 - 1
Accepted
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Submissions
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Acceptance Rate
37.3%

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