#### QUESTION:

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

items[i] = [valuei, weighti] where valuei represents the value and weighti represents the weight of the ith item. The value of each item in items is unique. Return a 2D integer array ret where ret[i] = [valuei, weighti], with weighti being the sum of weights of all items with value valuei.

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

**Example 1:**

```
Input: items1 = [[1,1],[4,5],[3,8]], items2 = [[3,1],[1,5]]
Output: [[1,6],[3,9],[4,5]]
Explanation:
The item with value = 1 occurs in items1 with weight = 1 and in items2 with weight = 5, total weight = 1 + 5 = 6.
The item with value = 3 occurs in items1 with weight = 8 and in items2 with weight = 1, total weight = 8 + 1 = 9.
The item with value = 4 occurs in items1 with weight = 5, total weight = 5.
Therefore, we return [[1,6],[3,9],[4,5]].
```

**Example 2:**

```
Input: items1 = [[1,1],[3,2],[2,3]], items2 = [[2,1],[3,2],[1,3]]
Output: [[1,4],[2,4],[3,4]]
Explanation:
The item with value = 1 occurs in items1 with weight = 1 and in items2 with weight = 3, total weight = 1 + 3 = 4.
The item with value = 2 occurs in items1 with weight = 3 and in items2 with weight = 1, total weight = 3 + 1 = 4.
The item with value = 3 occurs in items1 with weight = 2 and in items2 with weight = 2, total weight = 2 + 2 = 4.
Therefore, we return [[1,4],[2,4],[3,4]].
```

**Example 3:**

```
Input: items1 = [[1,3],[2,2]], items2 = [[7,1],[2,2],[1,4]]
Output: [[1,7],[2,4],[7,1]]
Explanation:
The item with value = 1 occurs in items1 with weight = 3 and in items2 with weight = 4, total weight = 3 + 4 = 7.
The item with value = 2 occurs in items1 with weight = 2 and in items2 with weight = 2, total weight = 2 + 2 = 4.
The item with value = 7 occurs in items2 with weight = 1, total weight = 1.
Therefore, we return [[1,7],[2,4],[7,1]].
```

**Constraints:**

```
1 <= items1.length, items2.length <= 1000
items1[i].length == items2[i].length == 2
1 <= valuei, weighti <= 1000
Each valuei in items1 is unique.
Each valuei in items2 is unique.
```

#### EXPLANATION:

easy的题目 ,for循环之后放入一个dictionary中, 对dictionary进行排序, 排序结束之后恢复成array就可以.

#### SOLUTION:

```
class Solution {
func mergeSimilarItems(_ items1: [[Int]], _ items2: [[Int]]) -> [[Int]] {
var dic:Dictionary<Int,Int> = [:]
for item in items1 {
if dic[item[0]] == nil {
dic[item[0]] = 0
}
dic[item[0]]! += item[1]
}
for item in items2 {
if dic[item[0]] == nil {
dic[item[0]] = 0
}
dic[item[0]]! += item[1]
}
return dic.sorted(by: { $0.key < $1.key }).map({[$0.key, $0.value]})
}
}
```