435. Non-overlapping Intervals

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435. Non-overlapping Intervals

Description

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.

Note that intervals which only touch at a point are non-overlapping . For example, [1, 2] and [2, 3] are non-overlapping.

Example 1:

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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:

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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:

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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 <= 10^5
  • intervals[i].length == 2
  • -5 * 10^4 <= starti < endi <= 5 * 10^4

Hints/Notes

  • 2025/01/08
  • greedy
  • No solution from 0x3F

Solution

Language: C++

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class Solution {
public:
    int eraseOverlapIntervals(vector<vector<int>>& intervals) {
        auto cmp = [](vector<int>& lhs, vector<int>& rhs) {
            return lhs[1] < rhs[1];
        };
        ranges::sort(intervals, cmp);
        int end = INT_MIN, res = 0, n = intervals.size();
        for (int i = 0; i < n; i++) {
            if (intervals[i][0] < end) {
                res++;
            } else {
                end = intervals[i][1];
            }
        }
        return res;
    }
};