Problem Description
Given two arrays of strings list1 and list2, find the common strings with the least index sum. A common string is a string that appeared in both list1 and list2. A common string with the least index sum is a common string such that if it appeared at list1[i] and list2[j] then i + j should be the minimum value among all the other common strings. Return all the common strings with the least index sum. Return the answer in any order.
Key Insights
- We need to find common elements in two lists.
- The index sum of common elements is crucial; we want to minimize this sum.
- A hash table (dictionary) can be used to store the indices of elements in one list for quick lookups in the other list.
- Multiple common elements can exist, hence we need to keep track of the minimum index sum and the corresponding elements.
Space and Time Complexity
Time Complexity: O(N + M) where N is the length of list1 and M is the length of list2 (due to iterating through both lists).
Space Complexity: O(N) for the hash table storing indices of list1.
Solution
We will use a hash table to store the indices of each string in list1. Then, we will iterate through list2 and check for common strings. For each common string, we will calculate the index sum and update our results accordingly. If we find a common string with a lesser index sum than previously recorded, we will reset our results. If it's the same sum, we will add it to our results.