Non-overlapping Intervals

Description

Given a collection of intervals, find the minimum number of intervals you need to remove to make the rest of the intervals non-overlapping.

 

Example 1:

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

Example 2:

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

Example 3:

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

 

Note:

1. You may assume the interval's end point is always bigger than its start point.
2. Intervals like [1,2] and [2,3] have borders "touching" but they don't overlap each other.

Solution(javascript)

const eraseOverlapIntervals = function (intervals = []) {
  if (!intervals.length) {
    return 0
  }
  intervals.sort((a, b) => a[1] - b[1])
  let prevEnd = intervals[0][1]
  let count = 1
  for (const [a, b] of intervals) {
    if (a >= prevEnd) {
      count += 1
      prevEnd = b
    }
  }
  return intervals.length - count
}