Problem
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 <= 10^5
Solution (Java)
class Solution {
// every base from 2 to n-1 of integer n
// must be a palindrome. This is pretty unlikely
public boolean isStrictlyPalindromic(int n) {
for(int i = 2; i < n-1; i++) {
// Integer.toString(int n, int i) converts n to base i
if(!isPalindrome(Integer.toString(n, i))) {
return false;
}
}
return true;
}
private boolean isPalindrome(String str) {
int left = 0;
int right = str.length()-1;
while(left < right) {
if(str.charAt(left) != str.charAt(right)) {
return false;
}
left++;
right--;
}
return true;
}
}
Explain:
nope.
Complexity:
- Time complexity : O(n).
- Space complexity : O(n).