Merge Similar Items

You are given two 2D integer arrays, items1 and items2, representing two sets of items. Each array items has the following properties:

• items[i] = [value<sub>i</sub>, weight<sub>i</sub>] where value<sub>i</sub> represents the value and weight<sub>i</sub> represents the weight of the i<sup>th</sup> item.

• The value of each item in items is unique.

Return a 2D integer array ret where ret[i] = [value<sub>i</sub>, weight<sub>i</sub>], with weight<sub>i</sub> being the sum of weights of all items with value value<sub>i</sub>.

Note: ret should be returned in ascending order by value.

LeetCode Problem - 2363

class Solution {
    public List<List<Integer>> mergeSimilarItems(int[][] items1, int[][] items2) {
        // Initialize the result list which will hold lists of merged items
        List<List<Integer>> result = new ArrayList<>();
        // Initialize a map to keep track of item values and their corresponding weights
        Map<Integer, Integer> mp = new HashMap<>();

        // Iterate over each item in items1
        for(int i = 0; i < items1.length; i++) {
            int value = items1[i][0], weight = items1[i][1];
            // Put the value and weight in the map
            mp.put(value, weight);
        }

        // Iterate over each item in items2
        for(int i = 0; i < items2.length; i++) {
            int value = items2[i][0], weight = items2[i][1];
            // Update the map: if the value already exists, add the weight; otherwise, put the value and weight
            mp.put(value, mp.getOrDefault(value, 0) + weight);
        }

        // Iterate over the keys in the map
        for(int e : mp.keySet()) {
            // Create a list to hold the current value and its total weight
            List<Integer> list = new ArrayList<>();
            int temp = mp.get(e);
            list.add(e);
            list.add(temp);
            // Add the list to the result
            result.add(list);
        }

        // Sort the result list based on the item values
        Collections.sort(result, new Comparator<List<Integer>>() {
            @Override
            public int compare(List<Integer> o1, List<Integer> o2) {
                return o1.get(0).compareTo(o2.get(0));
            }
        });

        // Return the sorted result list
        return result;
    }
}