find-longest-awesome-substring

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1542. Find Longest Awesome Substring (Hard)

You are given a string s. An awesome substring is a non-empty substring of s such that we can make any number of swaps in order to make it a palindrome.

Return the length of the maximum length awesome substring of s.

 

Example 1:

Input: s = "3242415"
Output: 5
Explanation: "24241" is the longest awesome substring, we can form the palindrome "24142" with some swaps.

Example 2:

Input: s = "12345678"
Output: 1

Example 3:

Input: s = "213123"
Output: 6
Explanation: "213123" is the longest awesome substring, we can form the palindrome "231132" with some swaps.

 

Constraints:

• 1 <= s.length <= 105
• s consists only of digits.

Related Topics

[Hash Table] [String] [Bit Manipulation]

Hints

Hint 1

Given the character counts, under what conditions can a palindrome be formed ?

Hint 2

From left to right, use bitwise xor-operation to compute for any prefix the number of times modulo 2 of each digit. (mask ^= (1<<(s[i]-'0')).

Hint 3

Expected complexity is O(n*A) where A is the alphabet (10).