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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.

Leetcode Link

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​

Python Code
class Solution (object):
    def eraseOverlapIntervals (self, intervals):
        if len(intervals) == 0:
            return 0
        intervals = sorted(intervals, key = lambda x:x[1])
        removeNum, curBorder = -1, intervals[0][1]
        for interval in intervals:
            if interval[0] < curBorder:
                removeNum += 1
            else:
                curBorder = interval[1]
        return removeNum