merge-intervals.js

/* Merge Intervals

Given an array of intervals where intervals[i] = [starti, endi], 
merge all overlapping intervals, and return an array of the non-overlapping
intervals that cover all the intervals in the input.

Example 1:
Input: intervals = [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into [1,6].

Example 2:
Input: intervals = [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [1,4] and [4,5] are considered overlapping.
 
Constraints:
1 <= intervals.length <= 104
intervals[i].length == 2
0 <= starti <= endi <= 104
*/

/**
 * @param {number[][]} intervals
 * @return {number[][]}
 */
 var merge = function(intervals) {
    let res = [];
    
    if(intervals.length <= 1 ){
        return intervals;
    }
    
    intervals.sort((a,b) => a[0] - b[0]);
    res.push(intervals[0]);
    
    for(let i = 1; i < intervals.length;i++){
        let resIndex = res.length - 1;
        
        if(res[resIndex][1] >= intervals[i][0]){
            res[resIndex][1] = Math.max(res[resIndex][1],intervals[i][1]);
        }else{
            res.push(intervals[i])            
        }
    }
    
    return res;
};