Evaluate the algorithmic complexity of the palindrome problem solution in terms of time and memory. If the alphabet is fixed (English letters, 26 characters), what is the memory complexity?

Checking whether a string is a palindrome is usually implemented by comparing characters from the beginning and end of the string, moving towards the center.

• In terms of time: the algorithm traverses the string at most once, comparing pairs of characters, so the time complexity is O(n), where n is the length of the string.
• In terms of memory: if no additional structures are created and characters are compared in place, no extra memory is required, which is O(1).

If the alphabet is fixed (for example, 26 English letters), and the task requires considering character frequencies or using auxiliary structures, then a fixed-size array of 26 elements can be allocated, which gives O(1) memory since the array size does not depend on the string length.

Example of palindrome check in Java:

boolean isPalindrome(String s) {
    int left = 0, right = s.length() - 1;
    while (left < right) {
        if (s.charAt(left) != s.charAt(right)) return false;
        left++;
        right--;
    }
    return true;
}