986. 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].

 

Input: firstList = [[0,2],[5,10],[13,23],[24,25]], secondList = [[1,5],[8,12],[15,24],[25,26]]
Output: [[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]

Example 2:

Input: firstList = [[1,3],[5,9]], secondList = []
Output: []

class Solution {

public int[][] intervalIntersection(int[][] firstList, int[][] secondList) {

List<int[]> res = new ArrayList<>();

int j=0;

int i=0;

while(i<firstList.length && j<secondList.length){

int left = Math.max(firstList[i][0],secondList[j][0]);

int right = Math.min(firstList[i][1],secondList[j][1]);

if(left<=right){

res.add(new int[]{left,right});

}

if(firstList[i][1]<secondList[j][1]){

i++;

}else{

j++;

}

}

return res.toArray(new int[res.size()][]);

}

}