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57. Insert Interval

You are given an array of non-overlapping intervals intervals where intervals[i] = [starti, endi] represent the start and the end of the i^th interval and intervals is sorted in ascending order by starti. You are also given an interval newInterval = [start, end] that represents the start and end of another interval

Example 1:

  • Input: intervals = [[1,3],[6,9]], newInterval = [2,5]
  • Output: [[1,5],[6,9]]

Example 2:

  • Input: intervals = [[1,2],[3,5],[6,7],[8,10],[12,16]], newInterval = [4,8]
  • Output: [[1,2],[3,10],[12,16]]
  • Explanation: Because the new interval [4,8] overlaps with [3,5],[6,7],[8,10].

Constraints:

  • 0 <= intervals.length <= 10^4
  • intervals[i].length == 2
  • 0 <= starti <= endi <= 10^5
  • intervals is sorted by starti in ascending order.
  • newInterval.length == 2
  • 0 <= start <= end <= 10^5

Solution

class Solution:
    def insert(
        self, intervals: list[list[int]], newInterval: list[int]
    ) -> list[list[int]]:
        result = []
        i, n = 0, len(intervals)
        start, end = newInterval

        # Everything before
        while i < n and intervals[i][1] < start:
            result.append(intervals[i])
            i += 1

        # Everything merged
        while i < n and intervals[i][0] <= end:
            start = min(start, intervals[i][0])
            end = max(end, intervals[i][1])
            i += 1
        result.append([start, end])

        # Everything after
        result.extend(intervals[i:])
        return result

Last updated on September 30, 2026

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