查看“︁69.Sqrt(x)”︁的源代码

=Description=
{{LeetCode
|id=sqrtx
|no=69
|difficulty=Easy
|category=Math
|collection=Top 150
|title=Sqrt(x)
|summary=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:

<syntaxhighlight lang="bash">
Input: x = 4
Output: 2
</syntaxhighlight>
Explanation: The square root of 4 is 2, so we return 2.
Example 2:

<syntaxhighlight lang="bash">
Input: x = 8
Output: 2
</syntaxhighlight>
Explanation: The square root of 8 is 2.82842..., and since we round it down to the nearest integer, 2 is returned.

===Binary search===
{{Submission|runtime=1ms|memory=40.82MB|rp=86.98|mp=40.25}}

<syntaxhighlight lang="bash">
class Solution {
    public int mySqrt(int x) {
        int l = 1, r = x;
        while(l <= r){
           int m = (r-l)/2 + l;
           if(m > x/m) r = m-1;
           else if(m < x/m) l = m+1;
           else return m;
        }
        return r;
    }
}
</syntaxhighlight>

[[Category:Algorithm]]
[[Category:Math]]
[[Category:LeetCode]]