main.go

// Source: https://leetcode.com/problems/count-days-without-meetings
// Title: Count Days Without Meetings
// Difficulty: Medium
// Author: Mu Yang <http://muyang.pro>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// You are given a positive integer `days` representing the total number of days an employee is available for work (starting from day 1). You are also given a 2D array `meetings` of size `n` where, `meetings[i] = [start_i, end_i]` represents the starting and ending days of meeting `i` (inclusive).
//
// Return the count of days when the employee is available for work but no meetings are scheduled.
//
// **Note:** The meetings may overlap.
//
// **Example 1:**
//
// ```
// Input: days = 10, meetings = [[5,7],[1,3],[9,10]]
// Output: 2
// Explanation:
// There is no meeting scheduled on the 4^th and 8^th days.
// ```
//
// **Example 2:**
//
// ```
// Input: days = 5, meetings = [[2,4],[1,3]]
// Output: 1
// Explanation:
// There is no meeting scheduled on the 5^th day.
// ```
//
// **Example 3:**
//
// ```
// Input: days = 6, meetings = [[1,6]]
// Output: 0
// Explanation:
// Meetings are scheduled for all working days.
// ```
//
// **Constraints:**
//
// - `1 <= days <= 10^9`
// - `1 <= meetings.length <= 10^5`
// - `meetings[i].length == 2`
// - `1 <= meetings[i][0] <= meetings[i][1] <= days`
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package main

import (
	"fmt"
	"slices"
)

func countDays(days int, meetings [][]int) int {
	slices.SortFunc(meetings, func(a, b []int) int {
		if a[0] != b[0] {
			return a[0] - b[0]
		}
		return a[1] - b[1]
	})

	count := 0
	now := 0
	for _, meeting := range meetings {
		count += max(meeting[0]-now-1, 0)
		now = max(now, meeting[1])
	}
	count += max(days-now, 0)

	return count
}

func main() {
	fmt.Println(countDays(
		10,
		[][]int{
			{5, 7},
			{1, 3},
			{9, 10},
		},

		// 5,
		// [][]int{
		// 	{1, 3},
		// 	{2, 4},
		// },
	))
}