28. Merge Intervals

class Solution:
    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
        intervals.sort(key=lambda x: x[0])         # by start
        res = []
        for s, e in intervals:
            if res and s <= res[-1][1]:            # overlaps the last merged interval
                res[-1][1] = max(res[-1][1], e)
            else:
                res.append([s, e])
        return res

class Solution {
    public int[][] merge(int[][] intervals) {
        Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
        List<int[]> res = new ArrayList<>();
        for (int[] cur : intervals) {
            if (!res.isEmpty() && cur[0] <= res.get(res.size() - 1)[1])
                res.get(res.size() - 1)[1] = Math.max(res.get(res.size() - 1)[1], cur[1]);
            else res.add(new int[]{cur[0], cur[1]});
        }
        return res.toArray(new int[0][]);
    }
}

class Solution {
public:
    vector<vector<int>> merge(vector<vector<int>>& intervals) {
        sort(intervals.begin(), intervals.end());
        vector<vector<int>> res;
        for (auto& cur : intervals) {
            if (!res.empty() && cur[0] <= res.back()[1]) res.back()[1] = max(res.back()[1], cur[1]);
            else res.push_back(cur);
        }
        return res;
    }
};

function merge(intervals) {
  intervals.sort((a, b) => a[0] - b[0]);
  const res = [];
  for (const [s, e] of intervals) {
    if (res.length && s <= res[res.length - 1][1]) res[res.length - 1][1] = Math.max(res[res.length - 1][1], e);
    else res.push([s, e]);
  }
  return res;
}