986. Interval List Intersections

Example 1

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: []

조건

0 <= firstList.length, secondList.length <= 1000
firstList.length + secondList.length >= 1
0 <= starti < endi <= 109
endi < starti+1
0 <= startj < endj <= 109
endj < startj+1

class Solution:
    def intervalIntersection(self, firstList: List[List[int]], secondList: List[List[int]]) -> List[List[int]]:
        n, m = len(firstList), len(secondList)
        l, r = 0, 0
        ans = []
        while l < n and r < m:
            out_list1 = max(firstList[l][0], secondList[r][0])
            out_list2 = min(firstList[l][1], secondList[r][1])
            
            if out_list2 - out_list1 >= 0:
                ans.append([out_list1, out_list2])
            if firstList[l][1] > secondList[r][1]:
                r += 1
            else:
                l += 1
        return ans