#2262 - Total Appeal of A String

Hard • View on LeetCode • View on GitHub

Problem Description

The appeal of a string is the number of distinct characters found in the string.

For example, the appeal of "abbca" is 3 because it has 3 distinct characters: 'a', 'b', and 'c'.

Given a string s, return the total appeal of all of its substrings.

A substring is a contiguous sequence of characters within a string.

Solution

/**
 * @param {string} s
 * @return {number}
 */
var appealSum = function(s) {
  const n = s.length;
  const lastSeen = new Array(26).fill(-1);
  let result = 0;

  for (let i = 0; i < n; i++) {
    const charIndex = s.charCodeAt(i) - 97;
    result += (i - lastSeen[charIndex]) * (n - i);
    lastSeen[charIndex] = i;
  }

  return result;
};