[Swift]LeetCode435. 无重叠区间 | Non-overlapping Intervals

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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:

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. 

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.

---

给定一个区间的集合，找到需要移除区间的最小数量，使剩余区间互不重叠。

注意:

1. 可以认为区间的终点总是大于它的起点。
2. 区间 [1,2] 和 [2,3] 的边界相互“接触”，但没有相互重叠。

示例 1:

输入: [ [1,2], [2,3], [3,4], [1,3] ]

输出: 1

解释: 移除 [1,3] 后，剩下的区间没有重叠。

示例 2:

输入: [ [1,2], [1,2], [1,2] ]

输出: 2

解释: 你需要移除两个 [1,2] 来使剩下的区间没有重叠。

示例 3:

输入: [ [1,2], [2,3] ]

输出: 0

解释: 你不需要移除任何区间，因为它们已经是无重叠的了。

---

76ms

/**
 * Definition for an interval.
 * public class Interval {
 *   public var start: Int
 *   public var end: Int
 *   public init(_ start: Int, _ end: Int) {
 *     self.start = start
 *     self.end = end
 *   }
 * }
 */
class Solution {
    func eraseOverlapIntervals(_ intervals: [Interval]) -> Int {
        var intervals = intervals
        if intervals.isEmpty {return 0}
        intervals.sort(by:{(_ a:Interval,_ b:Interval) -> Bool in return a.start < b.start})
        var res:Int = 0
        var n:Int = intervals.count
        var endLast:Int = intervals[0].end
        for i in 1..<n
        {
            var t:Int = endLast > intervals[i].start ? 1 : 0
            endLast = t == 1 ? min(endLast, intervals[i].end) : intervals[i].end
            res += t            
        }
        return res
    }
}

---

80ms

/**
 * Definition for an interval.
 * public class Interval {
 *   public var start: Int
 *   public var end: Int
 *   public init(_ start: Int, _ end: Int) {
 *     self.start = start
 *     self.end = end
 *   }
 * }
 */
class Solution {
    func eraseOverlapIntervals(_ intervals: [Interval]) -> Int {
        if intervals.count <= 1 {
            return 0
        }
        
        var move = 1
        var ts = intervals
        ts.sort { (i1, i2) -> Bool in
               return i1.end <= i2.end                         
          }

        var temp = ts[0]
        for i in 1..<ts.count {
            let start = ts[i].start
            if start >= temp.end {
                move += 1
                temp = ts[i]
            }
        }
        return intervals.count - move
    }
}