LeetCode:Valid Perfect Square
Valid Perfect Square
Total Accepted: 1976
Total Submissions: 5317
Difficulty: Medium
Given a positive integer num, write a function which returns True if num is a perfect square else False.
Note: Do not use any built-in library function such as
Example 1:
Example 2:
Credits: Special thanks to @elmirap for adding this problem and creating all test cases.
Subscribe to see which companies asked this question
Hide Tags
Binary Search
Hide Similar Problems
(M) Sqrt(x)
考え方:
二分検索
java code:
Total Accepted: 1976
Total Submissions: 5317
Difficulty: Medium
Given a positive integer num, write a function which returns True if num is a perfect square else False.
Note: Do not use any built-in library function such as
sqrt . Example 1:
Input: 16
Returns: True
Example 2:
Input: 14
Returns: False
Credits: Special thanks to @elmirap for adding this problem and creating all test cases.
Subscribe to see which companies asked this question
Hide Tags
Binary Search
Hide Similar Problems
(M) Sqrt(x)
考え方:
二分検索
java code:
public class Solution {
public boolean isPerfectSquare(int num) {
long lo = 1, hi = num / 2;
if(num == 1) return true;
long x = num;
while(lo <= hi) {
long mid = lo + (hi - lo) / 2;
if(mid * mid == x)
return true;
else if(mid * mid < x)
lo = mid + 1;
else
hi = mid - 1;
}
return false;
}
}