[Swift] Merge Intervals

Given an array of intervals where intervals[i] = [start$_i$, end$_i$], merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input.

Example 1:

Input: intervals = [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into [1,6].

Example 1:

Input: intervals = [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [1,4] and [4,5] are considered overlapping.

Constraints:

• 1 <= intervals.length <= 10$^4$
• intervals[i].length == 2
• 0 <= starti <= endi <= 10$^4$

풀러가기

문제 이해

코드

class Solution {
  func merge(_ intervals: [[Int]]) -> [[Int]] {
    if intervals.count < 2 {
      return intervals
    }
    
    var intervals = intervals.sorted { $0.first! < $1.first! }
    
    var ret: [[Int]] = []
    
    for i in 1 ..< intervals.count {
      let left = intervals[i - 1]
      var right = intervals[i]
      if left.last! >= right.first! && right.last! >= left.first! {
        right[0] = min(left[0], right[0])
        right[1] = max(left[1], right[1])
        intervals[i] = right
      } else {
        ret.append(left)
      }
    }
    ret.append(intervals.last!)
    
    return ret
  }
}

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