Interval List Intersections

Author: anantkaushik

986-interval-list-intersections.py

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+"""
+Problem Link: https://leetcode.com/problems/interval-list-intersections/
+
+Given two lists of closed intervals, each list of intervals is pairwise disjoint and in sorted order.
+Return the intersection of these two interval lists.
+(Formally, 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 is either empty, or can be represented as a closed interval.  
+For example, the intersection of [1, 3] and [2, 4] is [2, 3].)
+
+Example 1:
+Input: A = [[0,2],[5,10],[13,23],[24,25]], B = [[1,5],[8,12],[15,24],[25,26]]
+Output: [[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]
+Reminder: The inputs and the desired output are lists of Interval objects, and not arrays or lists.
+ 
+Note:
+0 <= A.length < 1000
+0 <= B.length < 1000
+0 <= A[i].start, A[i].end, B[i].start, B[i].end < 10^9
+"""
+class Solution:
+    def intervalIntersection(self, A: List[List[int]], B: List[List[int]]) -> List[List[int]]:
+      indexA = indexB = 0
+      res = []
+      while indexA < len(A) and indexB < len(B):
+        # startpoint of the intersection
+        start = max(A[indexA][0], B[indexB][0])
+        # endpoint of the intersection
+        end = min(A[indexA][1], B[indexB][1])
+        # if A and B intersect
+        if start <= end:
+          res.append([start,end])
+          
+        # Remove the interval with the smallest endpoint
+        if A[indexA][1] < B[indexB][1]:
+          indexA += 1
+        else:
+          indexB += 1
+      return res