Minimum Index Sum of Two Lists

Suppose Andy and Doris want to choose a restaurant for dinner, and they both have a list of favorite restaurants represented by strings.

You need to help them find out their common interest with the least list index sum. If there is a choice tie between answers, output all of them with no order requirement. You could assume there always exists an answer.

Example 1:

Input: list1 = ["Shogun","Tapioca Express","Burger King","KFC"], list2 = ["Piatti","The Grill at Torrey Pines","Hungry Hunter Steakhouse","Shogun"]
Output: ["Shogun"]
Explanation: The only restaurant they both like is "Shogun".

Example 2:

Input: list1 = ["Shogun","Tapioca Express","Burger King","KFC"], list2 = ["KFC","Shogun","Burger King"]
Output: ["Shogun"]
Explanation: The restaurant they both like and have the least index sum is "Shogun" with index sum 1 (0+1).

Constraints:

• 1 <= list1.length, list2.length <= 1000
• 1 <= list1[i].length, list2[i].length <= 30
• list1[i] and list2[i] consist of spaces ' ' and English letters.
• All the stings of list1 are unique.
• All the stings of list2 are unique.

SOLUTION:

class Solution:
    def findRestaurant(self, list1: List[str], list2: List[str]) -> List[str]:
        l1pos = {}
        l2pos = {}
        for i, num in enumerate(list1):
            l1pos[num] = i
        for i, num in enumerate(list2):
            l2pos[num] = i
        common = set.intersection(set(list1), set(list2))
        sums = {}
        for c in common:
            curr = l1pos[c] + l2pos[c]
            sums[curr] = sums.get(curr, []) + [c]
        return sums[min(sums.keys())]