countSubstrings = (s, count = 0) => {
    const tabu = initTabu(s);       /* Time O(N * N)  | Space O(N *  N) */

    count += singleLetters(s, tabu);/* Time O(N)      | Space O(N *  N) */
    count += doubleLetters(s, tabu);/* Time O(N)      | Space O(N *  N) */
    count += multiLetters(s, tabu); /* Time O(N *  N) | Space O(N *  N) */

    return count;
}
DP - Bottom Up
Matrix - Tabulation
2 Pointer - Slide Window
Time O(N^2) | Space O(N^2)
https://leetcode.com/problems/palindromic-substrings/
@param {string} s
@return {number}