Non-overlapping Intervals

LeetCode Q 435 - Non-overlapping Intervals

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

Note:

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

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: input types have been changed on April 15, 2019. Please reset to default code definition to get new method signature.

Solution

Code:

public int eraseOverlapIntervals(int[][] intervals) {
	Arrays.sort(intervals, (a,b) -> (a[1] - b[1]));

	int count = 0, curEnd = Integer.MIN_VALUE;
	for (int[] interval: intervals) {
		if (interval[0] >= curEnd)
			curEnd = interval[1];
		else
			count++;
	}

	return count;
}