LeetCode 1213. Intersection of Three Sorted Arrays

Description

https://leetcode.com/problems/intersection-of-three-sorted-arrays/

Given three integer arrays arr1arr2 and arr3 sorted in strictly increasing order, return a sorted array of only the integers that appeared in all three arrays.

Example 1:

Input: arr1 = [1,2,3,4,5], arr2 = [1,2,5,7,9], arr3 = [1,3,4,5,8]
Output: [1,5]
Explanation: Only 1 and 5 appeared in the three arrays.

Example 2:

Input: arr1 = [197,418,523,876,1356], arr2 = [501,880,1593,1710,1870], arr3 = [521,682,1337,1395,1764]
Output: []

Constraints:

  • 1 <= arr1.length, arr2.length, arr3.length <= 1000
  • 1 <= arr1[i], arr2[i], arr3[i] <= 2000

Explanation

Convert to sets and find intersections.

Python Solution

class Solution:
    def arraysIntersection(self, arr1: List[int], arr2: List[int], arr3: List[int]) -> List[int]:
        
        set1 = set(arr1)
        set2 = set(arr2)
        set3 = set(arr3)
        
        return sorted(set3.intersection(set1, set2))
  • Time Complexity: O(NlogN)
  • Space Complexity: O(N)

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