index.js

// score: 140
function optimizeIntervals(intervals) {
    return intervals
        .sort((x, y) => x[0] - y[0])
        .reduce((mergedIntervals, currentInterval) => {
            let [start, end] = currentInterval;

            let mergedInterval = mergedIntervals.at(-1);

            if (start <= mergedInterval?.[1]) {
                mergedIntervals.at(-1)[1] = Math.max(end, mergedInterval[1]);
            } else mergedIntervals.push(currentInterval);
            return mergedIntervals;
        }, []);
}

// score: 160
// function optimizeIntervals(intervals) {
//     intervals.sort((a, b) => a[0] - b[0]);

//     const result = [intervals[0]];

//     for (const val of intervals) {
//         const [start, end] = val;
//         const max = result[result.length - 1][1];

//         start > max
//             ? result.push(val)
//             : (result[result.length - 1][1] = Math.max(end, max));
//     }
//     return result;
// }

module.exports = optimizeIntervals;

console.log(optimizeIntervals([
    [5, 8],
    [2, 7],
    [3, 4]
])); // [[2, 8]]

console.log(optimizeIntervals([
    [1, 3],
    [8, 10],
    [2, 6]
])); // [[1, 6], [8, 10]]

console.log(optimizeIntervals([
    [3, 4],
    [1, 2],
    [5, 6]
])); // [[1, 2], [3, 4], [5, 6]]