57. Insert Interval #

Problem #

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

You may assume that the intervals were initially sorted according to their start times.

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].

Problem Summary #

This problem is an enhanced version of Problem 56. Given multiple non-overlapping intervals, and then another interval, merge any intervals that overlap.

Solution Approach #

It can be handled in 3 parts. First add the original intervals, that is, the intervals before the given newInterval. Then add newInterval; note that multiple intervals may need to be merged here. Finally, add the remaining original intervals to the final result.

Code #

package leetcode

/**
 * Definition for an interval.
 * type Interval struct {
 *	   Start int
 *	   End   int
 * }
 */

func insert(intervals []Interval, newInterval Interval) []Interval {
	res := make([]Interval, 0)
	if len(intervals) == 0 {
		res = append(res, newInterval)
		return res
	}
	curIndex := 0
	for curIndex < len(intervals) && intervals[curIndex].End < newInterval.Start {
		res = append(res, intervals[curIndex])
		curIndex++
	}

	for curIndex < len(intervals) && intervals[curIndex].Start <= newInterval.End {
		newInterval = Interval{Start: min(newInterval.Start, intervals[curIndex].Start), End: max(newInterval.End, intervals[curIndex].End)}
		curIndex++
	}
	res = append(res, newInterval)

	for curIndex < len(intervals) {
		res = append(res, intervals[curIndex])
		curIndex++
	}
	return res
}