s0986_interval_list_intersections.go

/*
	https://leetcode.com/problems/interval-list-intersections/

	You are given two lists of closed intervals, firstList and secondList, where
		firstList[i] = [starti, endi]
	and secondList[j] = [startj, endj]. Each list of intervals is pairwise disjoint
		and in sorted
	order.

	Return the intersection of these two interval lists.

	A closed interval [a, b] (with a <= b) denotes the set of real numbers x with a
		<= x <= b.

	The intersection of two closed intervals is a set of real numbers that are
		either empty or
	represented as a closed interval. For example, the intersection of [1, 3] and
		[2, 4] is [2, 3].
*/

package solutions

func intervalIntersection(firstList, secondList [][]int) [][]int {
	var res [][]int
	i, j := 0, 0

	for i < len(firstList) && j < len(secondList) {
		lo := Maximum(firstList[i][0], secondList[j][0])
		hi := Minimum(firstList[i][1], secondList[j][1])
		if lo <= hi {
			res = append(res, []int{lo, hi})
		}
		if firstList[i][1] < secondList[j][1] {
			i++
		} else {
			j++
		}
	}

	return res
}