A JS (ES6) function for this problem: https://www.interviewcake.com/question/merging-ranges

condense-meeting-times.js

// Take an array of meeting time ranges and return an array of condensed ranges
// https://www.interviewcake.com/question/merging-ranges

function condense_meeting_times(times) {
	let timeline = [];
	times.forEach((time) => {
		//time[0], time[1]
		// time is a tuple witih beginning and end
		if (timeline[time[0]] === undefined) {
			timeline[time[0]] = time[1];
			return;
		}
		// If start already exists, update its value if current end is greater
		if (timeline[time[0]] < time[1]) {
			timeline[time[0]] = time[1];
		}
	});
	let condensed_times = [];
	let time = [];
	timeline.forEach((end, start) => {
		// start is starting time, end is ending time
		// Initialize time period tracking
		if (!time.length) {
			time = [start, end];
			return;
		}
		// If start is greater than time[1]
		if (start > time[1]) {
			// Append previous time period
			condensed_times.push(time);
			// Start a new time period
			time = [start, end];
			return;
		}
		// If start is less than time[1]
		if (end > time[1]) {
			time[1] = end;
		}
	});
	// Append the last time period
	condensed_times.push(time);
	return condensed_times;
}

// Given
// [[0, 1], [3, 5], [4, 8], [10, 12], [9, 10]]
// Expect
// [[0, 1], [3, 8], [9, 12]]

export default condense_meeting_times;