LeetCode-in-All

56. Merge Intervals

Medium

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

Solution

class Solution {
public:
    vector<vector<int>> merge(vector<vector<int>>& intervals) {
        vector<vector<int>> ans;
        sort(intervals.begin(), intervals.end());
        vector<int> lastInterval = intervals[0];
        for (int i = 1; i < intervals.size(); i++) {
            if (intervals[i][0] > lastInterval[1]){
                ans.push_back(lastInterval);
                lastInterval = intervals[i];
            } else {
                lastInterval[1] = max(lastInterval[1], intervals[i][1]);
            }
        }
        ans.push_back(lastInterval);
        return ans;
    }
};

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