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Formatted question description: https://leetcode.ca/all/2396.html

2396. Strictly Palindromic Number

• Difficulty: Medium.
• Related Topics: Math, Two Pointers, Brainteaser.
• Similar Questions: Palindrome Number, Stone Game.

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 <= 105

Solution (Java, C++, Python)

• Java
• Python
• C++
• Go
• TypeScript
• RenderScript

• 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;
    }
  }
  
  ############
  
  class Solution {
      public boolean isStrictlyPalindromic(int n) {
          return false;
      }
  }
  

• class Solution:
      def isStrictlyPalindromic(self, n: int) -> bool:
          return False
  
  ############
  
  # 2396. Strictly Palindromic Number
  # https://leetcode.com/problems/strictly-palindromic-number/
  
  class Solution:
      def isStrictlyPalindromic(self, n: int) -> bool:
          
          def numberToBase(n, b):
              digits = []
              
              while n:
                  digits.append(n % b)
                  n //= b
                  
              return "".join(map(str, digits[::-1]))
          
          for k in range(2, n - 2 + 1):
              s = numberToBase(n, k)
              
              if s != s[::-1]:
                  return False
              
          return True
  
  

• class Solution {
  public:
      bool isStrictlyPalindromic(int n) {
          return false;
      }
  };
  

• func isStrictlyPalindromic(n int) bool {
  	return false
  }
  

• function isStrictlyPalindromic(n: number): boolean {
      return false;
  }
  
  

• impl Solution {
      pub fn is_strictly_palindromic(n: i32) -> bool {
          false
      }
  }
  
  

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).

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