3160.js

/** ------------------------------------------------------------------------------
 * 
 * 3160. Find the Number of Distinct Colors Among the Balls
 * Topics: Array, Hash Table
 * https://leetcode.com/problems/find-the-number-of-distinct-colors-among-the-balls/description/?envType=daily-question&envId=2025-02-07
 * 
 ------------------------------------------------------------------------------ */
/**
 * @param {number} limit
 * @param {number[][]} queries
 * @return {number[]}
 */
var queryResults = function (limit, queries) {
  const ball = new Map(),
    color = new Map(),
    answer = []
  let distinct = 0

  for (const [pos, c] of queries) {
    if (ball.has(pos)) {
      let prevColor = ball.get(pos)
      let cnt = color.get(prevColor) - 1
      if (cnt === 0) {
        color.delete(prevColor)
        distinct--
      } else {
        color.set(prevColor, cnt)
      }
    }

    ball.set(pos, c)
    let cnt = (color.get(c) || 0) + 1
    color.set(c, cnt)
    if (cnt === 1) distinct++

    answer.push(distinct)
  }

  return answer
}

console.log(
  queryResults(4, [
    [1, 1],
    [2, 2],
    [3, 3],
    [4, 4],
  ]),
)