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.

 

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.

Rust Solution

struct Solution;

impl Solution {
    fn erase_overlap_intervals(mut intervals: Vec<Vec<i32>>) -> i32 {
        if intervals.is_empty() {
            return 0;
        }
        let n = intervals.len();
        intervals.sort_by_key(|v| v[1]);
        let mut end = intervals[0][1];
        let mut res = 0;
        for i in 1..n {
            if intervals[i][0] < end {
                res += 1;
            } else {
                end = intervals[i][1];
            }
        }
        res
    }
}

#[test]
fn test() {
    let intervals = vec_vec_i32![[1, 2], [2, 3], [3, 4], [1, 3]];
    let res = 1;
    assert_eq!(Solution::erase_overlap_intervals(intervals), res);
    let intervals = vec_vec_i32![[1, 2], [1, 2], [1, 2]];
    let res = 2;
    assert_eq!(Solution::erase_overlap_intervals(intervals), res);
    let intervals = vec_vec_i32![[1, 2], [2, 3]];
    let res = 0;
    assert_eq!(Solution::erase_overlap_intervals(intervals), res);
}

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