LeetCode 1400. Construct K Palindrome Strings

原题链接在这里：https://leetcode.com/problems/construct-k-palindrome-strings/

题目：

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 <= 105
• s consists of lowercase English letters.
• 1 <= k <= 105

题解：

There are 2 conditions to fulfill.

One is k <= n. n = s.length(). We could break s into one single char String. But at most we could get n strings.

The other is the odd char count <= k. When there is a odd char, there must be another string containing it.

Time Complexity: O(n). n = s.length().

Space: O(1).

AC Java:

class Solution {
    public boolean canConstruct(String s, int k) {
        int n = s.length();
        int [] count = new int[26];
        int odd = 0;
        for(int i = 0; i < n; i++){
            int ind = s.charAt(i) - 'a';
            count[ind] ^= 1;
            odd += count[ind] == 1 ? 1 : -1;
        }
        
        return odd <= k && n >= k;
    }
}