3169.js

/** ------------------------------------------------------------------------------
 * 
 * 3169. Count Days Without Meetings
 * Topics: Array, Sorting
 * https://leetcode.com/problems/count-days-without-meetings/description/?envType=daily-question&envId=2025-03-24
 * 
 ------------------------------------------------------------------------------ */
/**
 * @param {number} days
 * @param {number[][]} meetings
 * @return {number}
 */
const countDays = (days, meetings) => {
  let res = 0
  meetings.sort((a, b) => (a[0] > b[0] ? 1 : -1))

  let lastFirst = 0

  for (let i = 1; i < meetings.length; i++) {
    lastFirst = Math.max(meetings[i - 1][1], lastFirst)
    const [firstNext, secondNext] = meetings[i]
    res = res + Math.max(0, firstNext - lastFirst - 1)
    lastFirst = Math.max(secondNext, lastFirst)
  }

  res = res + meetings[0][0] - 1 + days - Math.max(meetings.pop()[1], lastFirst)

  return res
}