LeetCode-in-Java
2396. Strictly Palindromic Number
Medium
An integer n is strictly palindromic if, for every base b between 2 and n - 2 (inclusive), the string representation of the integer n in base b is palindromic.
Given an integer n, return true if n is strictly palindromic and false otherwise.
A string is palindromic if it reads the same forward and backward.
Example 1:
Input: n = 9
Output: false
Explanation: In base 2: 9 = 1001 (base 2), which is palindromic.
In base 3: 9 = 100 (base 3), which is not palindromic.
Therefore, 9 is not strictly palindromic so we return false.
Note that in bases 4, 5, 6, and 7, n = 9 is also not palindromic.
Example 2:
Input: n = 4
Output: false
Explanation: We only consider base 2: 4 = 100 (base 2), which is not palindromic.
Therefore, we return false.
Constraints:
4 <= n <= 105
Solution
public class Solution {
public boolean isStrictlyPalindromic(int n) {
for (int i = 2; i <= n - 2; i++) {
String num = Integer.toString(i);
String s = baseConversion(num, 10, i);
if (!checkPalindrome(s)) {
return false;
}
}
return true;
}
private String baseConversion(String number, int sBase, int dBase) {
// Parse the number with source radix
// and return in specified radix(base)
return Integer.toString(Integer.parseInt(number, sBase), dBase);
}
private boolean checkPalindrome(String s) {
int start = 0;
int end = s.length() - 1;
while (start <= end) {
if (s.charAt(start) != s.charAt(end)) {
return false;
}
start++;
end--;
}
return true;
}
}