252. Meeting Rooms

At a Glance

Topic: intervals
Pattern: Merge Intervals (sort + pairwise check)
Difficulty: Easy
Companies: Amazon, Google, Facebook, Microsoft, Bloomberg
Frequency: High
LeetCode: 252

Problem (one-liner)

Given meeting intervals [start, end], determine whether one person could attend all meetings (no overlaps). Input: intervals. Output: boolean.

Recognition Cues

“Can attend all” → no overlap between consecutive meetings after sorting by start
Sort by start time, verify next.start >= previous.end (strictly >= for touching ok depending on statement—usually adjacent allowed)

Diagram

At-a-glance flow (replace with problem-specific Mermaid as you refine this note). camelCase node IDs; no spaces in IDs.

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Approaches

Check all pairs — O(n²) time.
Sort + linear scan — O(n log n) time / O(1) extra. <- pick this in interview.

Optimal Solution

Go

package main

import "sort"

func canAttendMeetings(intervals [][]int) bool {
	if len(intervals) <= 1 {
		return true
	}
	sort.Slice(intervals, func(left int, right int) bool {
		return intervals[left][0] < intervals[right][0]
	})
	for index := 1; index < len(intervals); index++ {
		previousEnd := intervals[index-1][1]
		currentStart := intervals[index][0]
		if currentStart < previousEnd {
			return false
		}
	}
	return true
}

JavaScript

function canAttendMeetings(intervals) {
	if (intervals.length <= 1) return true;
	const sorted = [...intervals].sort((left, right) => left[0] - right[0]);
	for (let index = 1; index < sorted.length; index++) {
		const previousEnd = sorted[index - 1][1];
		const currentStart = sorted[index][0];
		if (currentStart < previousEnd) return false;
	}
	return true;
}