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Java-based LeetCode algorithm problem solutions, regularly updated

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2722\. Join Two Arrays by ID

Medium

Given two arrays `arr1` and `arr2`, return a new array `joinedArray`. All the objects in each of the two inputs arrays will contain an `id` field that has an integer value. `joinedArray` is an array formed by merging `arr1` and `arr2` based on their `id` key. The length of `joinedArray` should be the length of unique values of `id`. The returned array should be sorted in **ascending** order based on the `id` key.

If a given `id` exists in one array but not the other, the single object with that `id` should be included in the result array without modification.

If two objects share an `id`, their properties should be merged into a single object:

*   If a key only exists in one object, that single key-value pair should be included in the object.
*   If a key is included in both objects, the value in the object from `arr2` should override the value from `arr1`.

**Example 1:**

**Input:** 

    arr1 = [ 
        {"id": 1, "x": 1}, 
        {"id": 2, "x": 9} 
    ], 
    arr2 = [ 
        {"id": 3, "x": 5} 
    ]

**Output:** 

    [ 
        {"id": 1, "x": 1}, 
        {"id": 2, "x": 9}, 
        {"id": 3, "x": 5} 
    ]

**Explanation:** There are no duplicate ids so arr1 is simply concatenated with arr2.

**Example 2:**

**Input:** 

    arr1 = [ 
        {"id": 1, "x": 2, "y": 3}, 
        {"id": 2, "x": 3, "y": 6} 
    ], 
    arr2 = [ 
        {"id": 2, "x": 10, "y": 20}, 
        {"id": 3, "x": 0, "y": 0} 
    ]

**Output:** 

    [ 
        {"id": 1, "x": 2, "y": 3}, 
        {"id": 2, "x": 10, "y": 20}, 
        {"id": 3, "x": 0, "y": 0} 
    ]

**Explanation:** The two objects with id=1 and id=3 are included in the result array without modifiction. The two objects with id=2 are merged together. The keys from arr2 override the values in arr1.

**Example 3:**

**Input:** 

    arr1 = [ 
        {"id": 1, "b": {"b": 94},"v": [4, 3], "y": 48} 
    ] 
    arr2 = [ 
        {"id": 1, "b": {"c": 84}, "v": [1, 3]} 
    ]

**Output:** 

    [ 
        {"id": 1, "b": {"c": 84}, "v": [1, 3], "y": 48} 
    ]

**Explanation:** The two objects with id=1 are merged together. For the keys "b" and "v" the values from arr2 are used. Since the key "y" only exists in arr1, that value is taken form arr1.

**Constraints:**

*   `arr1 and arr2 are valid JSON arrays`
*   `Each object in arr1 and arr2 has a unique integer id key`
*   2 <= JSON.stringify(arr1).length <= 10⁶
*   2 <= JSON.stringify(arr2).length <= 10⁶