435 Non-overlapping Intervals

Leetcode

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.

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.

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贪心算法。统计最多剩多少个，即可计算需要去掉多少个。按右边界排序，找到下一个右边界最小且不与当前右边界重叠的，计数并更新右边界。

public int eraseOverlapIntervals(int[][] intervals) {
    Arrays.sort(intervals,new Comparator<int[]>(){
        public int compare(int[] arr1, int[] arr2){
            return arr1[1]-arr2[1];
        }
    });
    int count=1;
    int right=intervals[0][1];
    for(int i=1;i<intervals.length;++i){
        if(intervals[i][0]>=right){
            count++;
            right=intervals[i][1];
        }
    }
    return intervals.length-count;
}