Intersection of Multiple Arrays

Problem Description

Given a 2D integer array nums where nums[i] is a non-empty array of distinct positive integers, return the list of integers that are present in each array of nums sorted in ascending order.

Key Insights

• The problem requires finding common elements across multiple arrays.
• Since all elements in each individual array are distinct, we can use a frequency count to track occurrences.
• A hash table (or dictionary) can efficiently count how many times each integer appears across all arrays.
• The final result should be sorted in ascending order.

Space and Time Complexity

Time Complexity: O(n + k log k), where n is the total number of integers across all arrays and k is the number of common integers found.
Space Complexity: O(n), for storing the counts of integers.

Solution

To solve the problem, we can use the following approach:

1. Use a hash table to count occurrences of each integer across all arrays.
2. Iterate through each array and update the counts for each integer.
3. After processing all arrays, filter the integers that appear in all arrays (i.e., have counts equal to the number of arrays).
4. Finally, sort the result and return it.

Code Solutions