0056-merge-intervals.js

/**
 * https://leetcode.com/problems/merge-intervals/
 * Time O(N * logN) | Space O(N)
 * @param {number[][]} intervals
 * @return {number[][]}
 */
var merge = function (intervals) {
    intervals.sort(([aStart, aEnd], [bStart, bEnd]) =>
        aStart !== bStart ? aStart - bStart : aEnd - bEnd
    );

    return mergerInterval(intervals);
};

const mergerInterval = (intervals, merged = []) => {
    let prev = intervals.shift();

    for (const curr of intervals) {
        const [prevStart, prevEnd] = prev;
        const [currStart, currEnd] = curr;

        const hasOverlap = currStart <= prevEnd;
        if (hasOverlap) {
            prev[1] = Math.max(prev[1], curr[1]);
            continue;
        }

        merged.push(prev);
        prev = curr;
    }

    return [...merged, prev];
};