1358.js

/** ------------------------------------------------------------------------------
 * 
 * 1358. Number of Substrings Containing All Three Characters
 * Topics: Hash Table, Sliding Window
 * https://leetcode.com/problems/number-of-substrings-containing-all-three-characters/description/?envType=daily-question&envId=2025-03-11
 * 
 ------------------------------------------------------------------------------ */
/**
 * @param {string} s
 * @return {number}
 */
var numberOfSubstrings = function (s) {
  let a = -1,
    b = -1,
    c = -1,
    count = 0
  for (let i = 0; i < s.length; i++) {
    switch (s[i]) {
      case "a":
        a = i
        break
      case "b":
        b = i
        break
      case "c":
        c = i
        break
    }

    if (a === -1 || b === -1 || c === -1) {
      continue
    }

    const min = Math.min(a, b, c)
    count += min + 1
  }

  return count
}

console.log(numberOfSubstrings("abcabc"))

/**
 * @param {string} s
 * @return {number}
 */
var numberOfSubstrings2 = function (s) {
  let count = { a: 0, b: 0, c: 0 } // Track character count
  let left = 0,
    result = 0

  for (let right = 0; right < s.length; right++) {
    count[s[right]]++ // Expand window

    // When all characters are in the window, move left pointer
    while (count["a"] > 0 && count["b"] > 0 && count["c"] > 0) {
      result += s.length - right // All substrings from left to end are valid
      count[s[left]]--
      left++ // Shrink window
    }
  }

  return result
}