Valid Perfect Square (E)
題目
Given a positive integer num, write a function which returns True if num is a perfect square else False.
Follow up: Do not use any built-in library function such as sqrt.
Example 1:
Input: num = 16
Output: true
Example 2:
Input: num = 14
Output: false
Constraints:
1 <= num <= 2^31 - 1
題意
判斷一個整數是不是完全平方數，要求不能用內置方法，
思路
二分法，注意值越界問題，
代碼實作
Java
class Solution {
public boolean isPerfectSquare(int num) {
long left = 1, right = num;
while (left <= right) {
long mid = (right - left) / 2 + left;
if (mid * mid > num) {
right = mid - 1;
} else if (mid * mid < num) {
left = mid + 1;
} else {
return true;
}
}
return false;
}
}
轉載請註明出處，本文鏈接：https://www.uj5u.com/qita/27707.html
標籤：其他