solves #2363: Merge Similar Items in java

Author: anishLearnsToCode

README.md

@@ -757,7 +757,7 @@
 | 2351 | [First Letter to Appear Twice](https://leetcode.com/problems/first-letter-to-appear-twice)                                                                             |                                                                                  [![Java](assets/java.png)](src/FirstLetterToAppearTwice.java)                                                                                   |                                                                                                                                   |
 | 2357 | [Make Array Zero by Subtracting Equal Amounts](https://leetcode.com/problems/make-array-zero-by-subtracting-equal-amounts)                                             |                                                                           [![Java](assets/java.png)](src/MakeArrayZeroBySubtractingEqualAmounts.java)                                                                            |                                                                                                                                   |
 | 2360 | [Longest Cycle in a Graph](https://leetcode.com/problems/longest-cycle-in-a-graph)                                                                                     |                                                                                 [![Python](assets/python.png)](python/longest_cycle_in_graph.py)                                                                                 |                                                                                                                                   |
-| 2363 | [Merge Similar Items](https://leetcode.com/problems/merge-similar-items)                                                                                               |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 2363 | [Merge Similar Items](https://leetcode.com/problems/merge-similar-items)                                                                                               |                                                                                      [![Java](assets/java.png)](src/MergeSimilarItems.java)                                                                                      |                                                                                                                                   |
 | 2367 | [Number of Arithmetic Triplets](https://leetcode.com/problems/number-of-arithmetic-triplets)                                                                           |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 2373 | [Largest Local Values in a Matrix](https://leetcode.com/problems/largest-local-values-in-a-matrix)                                                                     |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 2379 | [Minimum Recolors to Get K Consecutive Black Blocks](https://leetcode.com/problems/minimum-recolors-to-get-k-consecutive-black-blocks)                                 |                                                                                                                                                                                                                                  |                                                                                                                                   |

src/MergeSimilarItems.java

@@ -0,0 +1,42 @@
+// https://leetcode.com/problems/merge-similar-items
+// T: O(Nlog(N))
+// S: O(N)
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class MergeSimilarItems {
+    public List<List<Integer>> mergeSimilarItems(int[][] items1, int[][] items2) {
+        final Map<Integer, Integer> valueToWeight = getValueToWeightMapping(items1);
+        for (int[] row : items2) {
+            if (valueToWeight.containsKey(row[0])) {
+                valueToWeight.put(row[0], valueToWeight.get(row[0]) + row[1]);
+            } else {
+                valueToWeight.put(row[0], row[1]);
+            }
+        }
+
+        final List<List<Integer>> list = toList(valueToWeight);
+        list.sort(Comparator.comparingInt(a -> a.get(0)));
+        return list;
+    }
+
+    private List<List<Integer>> toList(Map<Integer, Integer> mapping) {
+        final List<List<Integer>> result = new ArrayList<>();
+        for (Map.Entry<Integer, Integer> entry : mapping.entrySet()) {
+            result.add(List.of(entry.getKey(), entry.getValue()));
+        }
+        return result;
+    }
+
+    private Map<Integer, Integer> getValueToWeightMapping(int[][] array) {
+        final Map<Integer, Integer> result = new HashMap<>();
+        for (int[] row : array) {
+            result.put(row[0], row[1]);
+        }
+        return result;
+    }
+}