Minimum Index Sum of Two Lists.py

'''
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:
["Shogun", "Tapioca Express", "Burger King", "KFC"]
["Piatti", "The Grill at Torrey Pines", "Hungry Hunter Steakhouse", "Shogun"]
Output: ["Shogun"]
Explanation: The only restaurant they both like is "Shogun".
Example 2:
Input:
["Shogun", "Tapioca Express", "Burger King", "KFC"]
["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).
Note:
The length of both lists will be in the range of [1, 1000].
The length of strings in both lists will be in the range of [1, 30].
The index is starting from 0 to the list length minus 1.
No duplicates in both lists.
'''

class Solution(object):
    def findRestaurant(self, list1, list2):
        """
        :type list1: List[str]
        :type list2: List[str]
        :rtype: List[str]
        """
        
        if len(list1) < len(list2):
            return self.findRestaurant(list2, list1)
        
        key_to_idx = {}
        for i in xrange(len(list2)):
            key_to_idx[list2[i]] = i
            
        res = []
        idx_sum = float('inf')
        
        for i in xrange(len(list1)):
            if list1[i] in key_to_idx:
                tmp = i + key_to_idx[list1[i]]
                if tmp < idx_sum:
                    res = [list1[i]]
                    idx_sum = tmp
                elif tmp == idx_sum:
                    res.append(list1[i])
                    
        return res