Java

  • import java.util.ArrayList;
    import java.util.Arrays;
    import java.util.HashMap;
    import java.util.Map.Entry;
    
    
    /*
    
    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.
    
    
     */
    
    public class Minimum_Index_Sum_of_Two_Lists {
    
    	public static void main(String[] args) {
    		Minimum_Index_Sum_of_Two_Lists out = new Minimum_Index_Sum_of_Two_Lists();
    		Solution s = out.new Solution();
    
    		String[] s1 = new String[]{"Shogun","Tapioca Express","Burger King","KFC"};
    		String[] s2 = new String[]{"KFC","Burger King","Tapioca Express","Shogun"};
    		System.out.println(Arrays.toString(s.findRestaurant(s1, s2)));
    
    		Solution2 sl2 = out.new Solution2();
    
    		String[] s21 = new String[]{"Shogun","Tapioca Express","Burger King","KFC"};
    		String[] s22 = new String[]{"KFC","Burger King","Tapioca Express","Shogun"};
    		System.out.println(Arrays.toString(sl2.findRestaurant(s21, s22)));
    	}
    
        // o(n^2)
    	public class Solution {
    	    public String[] findRestaurant(String[] list1, String[] list2) {
    	        if (list1 == null || list2 == null || list1.length == 0 || list2.length == 0) {
    	            return new String[]{""};
    	        }
    
    	        // maintain 2 indexes, both pointing to the same restaurant
    	        int index1 = -1; // minus: not-found
    	        int index2 = -1;
    	        int min = Integer.MAX_VALUE;
    	        ArrayList<String> restaurant = new ArrayList<String>(30); // length of strings 1-30
    
    	        for (int i = 0; i < list1.length; i++) {
    	            for (int j = 0; j < list2.length; j++) {
    	                if (list1[i].equals(list2[j]) && (i + j < min)) {
    	                    // record indexes
    	                    min = i + j;
    	                    restaurant = new ArrayList<String>(30);
    	                    restaurant.add(list1[i]);
    	                } else if (list1[i].equals(list2[j]) && (i + j == min)) {
    	                    // choice tie, then print all of them
    	                    restaurant.add(list1[i]);
    	                }
    	            }
    	        }
    
    	        return restaurant.toArray(new String[restaurant.size()]);
    
    	        // @note: below has runtime error: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.String;
    	        //return (String[]) restaurant.toArray();
    	    }
    	}
    
    	// o(m+n), extra space
    	public class Solution2 {
    	    public String[] findRestaurant(String[] list1, String[] list2) {
    	        if (list1 == null || list2 == null || list1.length == 0 || list2.length == 0) {
    	            return new String[]{""};
    	        }
    
    	        // maintain 2 indexes, both pointing to the same restaurant
    	        int index1 = -1; // minus: not-found
    	        int index2 = -1;
    	        int min = Integer.MAX_VALUE;
    	        ArrayList<String> restaurant = new ArrayList<String>(30); // length of strings 1-30
    
    	        // @note: use 2 hashmap: 1.store name => index, 2.store sumIndex => word
    
    	        // store list1 for o(1) access
    	        HashMap<String, Integer> hmList1 = new HashMap<>();
    	        for (int i = 0; i < list1.length; i++) {
    	            hmList1.put(list1[i], i);
    	        }
    
    	        // store sumIndex => word
    	        int minIndex = Integer.MAX_VALUE;
    	        for (int j = 0; j < list2.length; j++) {
    	            if (hmList1.containsKey(list2[j])) {
    	                // common interest
    	                int sum = j + hmList1.get(list2[j]);
    		            if (sum < minIndex) {
    		            	minIndex = sum; // update minIndex
    
    		            	restaurant = new ArrayList<String>(30);
    		            	restaurant.add(list2[j]);
    		            } else if (sum == minIndex) {
    		            	restaurant.add(list2[j]);
    		            }
    	            }
    	        }
    
    	        return restaurant.toArray(new String[restaurant.size()]);
    	    }
    	}
    }
    
  • // OJ: https://leetcode.com/problems/minimum-index-sum-of-two-lists/
    // Time: O(L1 + L2)
    // Space: O(L1)
    class Solution {
    public:
        vector<string> findRestaurant(vector<string>& list1, vector<string>& list2) {
            unordered_map<string, int> m;
            for (int i = 0; i < list1.size(); ++i) m[list1[i]] = i;
            int minSum = INT_MAX;
            vector<string> ans;
            for (int i = 0; i < list2.size() && i <= minSum; ++i) {
                if (m.find(list2[i]) == m.end() || i + m[list2[i]] > minSum) continue;
                if (i + m[list2[i]] < minSum) {
                    ans.clear();
                    minSum = i + m[list2[i]];
                }
                ans.push_back(list2[i]);
            }
            return ans;
        }
    };
    
  • class Solution(object):
      def findRestaurant(self, list1, list2):
        """
        :type list1: List[str]
        :type list2: List[str]
        :rtype: List[str]
        """
        minSum = float("inf")
        ans = []
        d = {}
        for i, name in enumerate(list2):
          d[name] = i
        for i, name in enumerate(list1):
          idxSum = i + d.get(name, float("inf"))
          if idxSum == minSum:
            ans.append(name)
          if idxSum < minSum:
            ans = [name]
            minSum = idxSum
        return ans
    
    

Java

  • class Solution {
        public String[] findRestaurant(String[] list1, String[] list2) {
            int length1 = list1.length, length2 = list2.length;
            int leastIndexSum = Integer.MAX_VALUE;
            Map<String, Integer> list1Map = new HashMap<String, Integer>();
            Map<Integer, List<String>> indexSumInterestMap = new HashMap<Integer, List<String>>();
            for (int i = 0; i < length1; i++)
                list1Map.put(list1[i], i);
            for (int i = 0; i < length2; i++) {
                String interest = list2[i];
                if (!list1Map.containsKey(interest))
                    continue;
                int indexSum = list1Map.get(interest) + i;
                List<String> interests = indexSumInterestMap.getOrDefault(indexSum, new ArrayList<String>());
                interests.add(interest);
                indexSumInterestMap.put(indexSum, interests);
                if (indexSum < leastIndexSum)
                    leastIndexSum = indexSum;
            }
            List<String> interestsList = indexSumInterestMap.getOrDefault(leastIndexSum, new ArrayList<String>());
            int length = interestsList.size();
            String[] interests = new String[length];
            for (int i = 0; i < length; i++)
                interests[i] = interestsList.get(i);
            return interests;
        }
    }
    
  • // OJ: https://leetcode.com/problems/minimum-index-sum-of-two-lists/
    // Time: O(L1 + L2)
    // Space: O(L1)
    class Solution {
    public:
        vector<string> findRestaurant(vector<string>& list1, vector<string>& list2) {
            unordered_map<string, int> m;
            for (int i = 0; i < list1.size(); ++i) m[list1[i]] = i;
            int minSum = INT_MAX;
            vector<string> ans;
            for (int i = 0; i < list2.size() && i <= minSum; ++i) {
                if (m.find(list2[i]) == m.end() || i + m[list2[i]] > minSum) continue;
                if (i + m[list2[i]] < minSum) {
                    ans.clear();
                    minSum = i + m[list2[i]];
                }
                ans.push_back(list2[i]);
            }
            return ans;
        }
    };
    
  • class Solution(object):
      def findRestaurant(self, list1, list2):
        """
        :type list1: List[str]
        :type list2: List[str]
        :rtype: List[str]
        """
        minSum = float("inf")
        ans = []
        d = {}
        for i, name in enumerate(list2):
          d[name] = i
        for i, name in enumerate(list1):
          idxSum = i + d.get(name, float("inf"))
          if idxSum == minSum:
            ans.append(name)
          if idxSum < minSum:
            ans = [name]
            minSum = idxSum
        return ans
    
    

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