LeetCode 2722: Join Two Arrays by ID Solution

Master LeetCode problem 2722 (Join Two Arrays by ID), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2722. Join Two Arrays by ID

Medium

Problem Explanation

Explanation

To solve this problem, we will iterate over both input arrays and merge the objects based on their id keys. We will use a hash map to store the merged objects based on their id. When merging two objects with the same id, we will prioritize the values from arr2 over arr1. Finally, we will convert the hash map to a list and sort it based on the id key.

Time complexity: O(n)
Space complexity: O(n)

Solution Code

import java.util.*;

class Solution {
    public List<Map<String, Object>> joinArrays(List<Map<String, Object>> arr1, List<Map<String, Object>> arr2) {
        Map<Integer, Map<String, Object>> mergedMap = new HashMap<>();
        
        for (Map<String, Object> obj : arr1) {
            mergedMap.put((Integer) obj.get("id"), obj);
        }
        
        for (Map<String, Object> obj : arr2) {
            int id = (Integer) obj.get("id");
            if (mergedMap.containsKey(id)) {
                Map<String, Object> mergedObj = mergedMap.get(id);
                for (Map.Entry<String, Object> entry : obj.entrySet()) {
                    mergedObj.put(entry.getKey(), entry.getValue());
                }
            } else {
                mergedMap.put(id, obj);
            }
        }
        
        List<Map<String, Object>> result = new ArrayList<>(mergedMap.values());
        result.sort(Comparator.comparingInt(obj -> (Integer) obj.get("id")));
        
        return result;
    }
}

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