leetcode - 1400. Construct K Palindrome Strings

Description

Given a string s and an integer k, return true if you can use all the characters in s to construct k palindrome strings or false otherwise.

Example 1:

Input: s = "annabelle", k = 2
Output: true
Explanation: You can construct two palindromes using all characters in s.
Some possible constructions "anna" + "elble", "anbna" + "elle", "anellena" + "b"

Example 2:

Input: s = "leetcode", k = 3
Output: false
Explanation: It is impossible to construct 3 palindromes using all the characters of s.

Example 3:

Input: s = "true", k = 4
Output: true
Explanation: The only possible solution is to put each character in a separate string.

Constraints:

1 <= s.length <= 10^5
s consists of lowercase English letters.
1 <= k <= 10^5

Solution

To make k palindromes, we could have at most k odd characters, go through the string and calculate the count of odd characters, then compare with k.

One corner case: if k is larger than the length of the string, we need to return False

Time complexity: $o(n)$
Space complexity: $o(n)$

Code

class Solution:
    def canConstruct(self, s: str, k: int) -> bool:
        str_cnt = collections.Counter(s)
        odd_cnt = 0
        for ch, cnt in str_cnt.items():
            odd_cnt += (cnt & 1 == 1)
        return odd_cnt <= k <= len(s)