message: Update construct-k-palindrome-strings.cpp
diff: // Space: O(1)
  class Solution {
  +public:
  + bool canConstruct(string s, int k) {
  + bitset<26> odd;
  + for (const auto& c : s) {
  + odd.flip(c - 'a');
  + }
  + return odd.count() <= k && k <= s.length();
  + }
  +};
  +
  +// Time: O(n)
  +// Space: O(1)
  +class Solution2 {
  public:
  bool canConstruct(string s, int k) {
  const auto& count = counter(s);
  