3272. Find the Count of Good Integers
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You are given two positive integers n and k.
An integer x is called k-palindromic if:
xis a palindrome.xis divisible byk.
An integer is called good if its digits can be rearranged to form a k-palindromic integer. For example, for k = 2, 2020 can be rearranged to form the k-palindromic integer 2002, whereas 1010 cannot be rearranged to form a k-palindromic integer.
Return the count of good integers containing n digits.
Note that any integer must not have leading zeros, neither before nor after rearrangement. For example, 1010 cannot be rearranged to form 101.
Example 1:
Input: n = 3, k = 5
Output: 27
Explanation:
Some of the good integers are:
- 551 because it can be rearranged to form 515.
- 525 because it is already k-palindromic.
Example 2:
Input: n = 1, k = 4
Output: 2
Explanation:
The two good integers are 4 and 8.
Example 3:
Input: n = 5, k = 6
Output: 2468
Constraints:
1 <= n <= 101 <= k <= 9
Hints
Hint 1
How to generate all K-palindromic strings of length
n? Do we need to go through all n digits?Hint 2
Use permutations to calculate the number of possible rearrangements.