Leetcode

Longest Palindrome

  • Time:O(n)
  • Space:O(128) = O(1)

C++

class Solution {
 public:
  int longestPalindrome(string s) {
    int ans = 0;
    vector<int> count(128);

    for (const char c : s)
      ++count[c];

    for (const int c : count)
      ans += c % 2 == 0 ? c : c - 1;

    const bool hasOddCount =
        any_of(begin(count), end(count), [](int c) { return c & 1; });

    return ans + hasOddCount;
  }
};

JAVA

class Solution {
  public int longestPalindrome(String s) {
    int ans = 0;
    int[] count = new int[128];

    for (final char c : s.toCharArray())
      ++count[c];

    for (final int c : count)
      ans += c % 2 == 0 ? c : c - 1;

    final boolean hasOddCount = Arrays.stream(count).anyMatch(c -> c % 2 == 1);

    return ans + (hasOddCount ? 1 : 0);
  }
}

Python

class Solution:
  def longestPalindrome(self, s: str) -> int:
    ans = 0
    count = Counter(s)

    for c in count.values():
      ans += c if c % 2 == 0 else c - 1

    hasOddCount = any(c % 2 == 1 for c in count.values())

    return ans + hasOddCount