0435: Non-overlapping Intervals

Problem Statement

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.

Note that intervals which only touch at a point are non-overlapping. For example, [1, 2] and [2, 3] are 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

Code Solution

class Solution:
    def eraseOverlapIntervals(self, intervals):
        
        intervals.sort(key=lambda x: (x[1], x[0]))
        
        count = 0
        prev = intervals[0]
        for ix in range(1, len(intervals)):
            curr = intervals[ix]
            if prev[1] > curr[0]:
                count = count + 1
                continue
            prev = curr
        
        return count