435. Non-overlapping Intervals

Description

Given an array of intervals intervals where intervals[i] = [starti, endi], return the minimum number of intervals you need to remove to make the rest of the intervals non-overlapping.

 

Example 1:

Input: intervals = [[1,2],[2,3],[3,4],[1,3]]
Output: 1
Explanation: [1,3] can be removed and the rest of the intervals are non-overlapping.

Example 2:

Input: intervals = [[1,2],[1,2],[1,2]]
Output: 2
Explanation: You need to remove two [1,2] to make the rest of the intervals non-overlapping.

Example 3:

Input: intervals = [[1,2],[2,3]]
Output: 0
Explanation: You don't need to remove any of the intervals since they're already non-overlapping.

 

Constraints:

• 1 <= intervals.length <= 105
• intervals[i].length == 2
• -5 * 104 <= starti < endi <= 5 * 104

Solution

non-overlapping-intervals.py

class Solution:
    def eraseOverlapIntervals(self, intervals: List[List[int]]) -> int:

        n = len(intervals)

        if n < 2: return 0

        intervals.sort(key = lambda x : x[0])

        last = intervals[0][1]
        count = 0

        for pairs in intervals[1:]:
            if pairs[0] < last:
                count += 1
                last = min(pairs[1], last)

            else:
                last = pairs[1]



        return count