69. Sqrt(x)

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69. Sqrt(x)

Description

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:

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

Example 2:

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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 <= 2^31 - 1

Hints/Notes

Solution

Language: C++

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class Solution {
public:
    int mySqrt(int x) {
        int left = -1, right = 2 << 16;
        while (left + 1 < right) {
            long mid = (left + right) / 2;
            if (mid * mid == x) {
                return mid;
            } else if (mid * mid < x) {
                left = mid;
            } else {
                right = mid;
            }
        }
        return left;
    }
};