0435-non-overlapping-intervals.java

public class Solution {

    public int eraseOverlapIntervals(int[][] intervals) {
        int intervalsRemoved = 0;

        Arrays.sort(
            intervals,
            (arr1, arr2) -> Integer.compare(arr1[0], arr2[0])
        );

        int[] intervalFirst = intervals[0];

        for (int i = 1; i < intervals.length; i++) {
            if (firstIntervalwithinSecond(intervalFirst, intervals[i])) {
                //mark first interval to be removed
                intervalsRemoved++;
                // determine which interval to remove
                //remove the interval that ends last
                if (intervalFirst[1] > intervals[i][1]) {
                    intervalFirst = intervals[i];
                }
            } else {
                intervalFirst = intervals[i];
            }
        }
        return intervalsRemoved;
    }

    public boolean firstIntervalwithinSecond(
        int[] intervalFirst,
        int[] intervalSecond
    ) {
        return intervalSecond[0] < intervalFirst[1];
    }
}