 # 867. Transpose Matrix

Given a 2D integer array `matrix`, return the transpose of `matrix`.

The transpose of a matrix is the matrix flipped over its main diagonal, switching the matrix’s row and column indices.

Example 1:

`Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]Output: [[1,4,7],[2,5,8],[3,6,9]]`

Example 2:

`Input: matrix = [[1,2,3],[4,5,6]]Output: [[1,4],[2,5],[3,6]]`
`class Solution {public…`

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# 136. Single Number

Given a non-empty array of integers `nums`, every element appears twice except for one. Find that single one.

You must implement a solution with a linear runtime complexity and use only constant extra space.

Example 1:

`Input: nums = [2,2,1]Output: 1`

Example 2:

`Input: nums = [4,1,2,1,2]Output: 4`

Example 3:

`Input: nums = Output: 1`

constant extra space

## 解法一

`class Solution {public:    int singleNumber(vector<int>& nums) {                int arr_pos[3*10000+1] = {0};        int arr_neg[3*10000] = {0};                for(int i=0; i<nums.size(); i++){            if(nums[i] >= 0){                arr_pos[nums[i]]++;            }            else{                arr_neg[-(nums[i])]++;            }        }               for(int i=0; i<=3*10000; i++){            if(arr_pos[i] == 1){                return i;            }                        if(arr_neg[i] == 1){                    return -i;            }        }        return 0;    }};`

## 解法二

`Input: nums = [4,1,2,1,2]Output: 4`

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# Spinner 下拉式選單

1. 在strings.xml中建立字串陣列，再將此字串陣列設定給spinner元件成為選單
`<resources>    <string name="app_name">spinner</string>    <string-array name="gender_list">        <item>男生</item>        <item>女生</item>    </string-array></resources>`

2. 在介面布局檔(activity_main.xml)中加入spinner元件，並設定好屬性

`<Spinner    android:id="@+id/spnGender"    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:layout_marginLeft="20dp"    android:layout_marginTop="20dp"    android:entries="@array/gender_list" />`

3. MainActivity.java中取得spiinner元件，並設定處理程序

`@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    Spinner mspnGender = findViewById(R.id.spnGender);    mspnGender.setOnItemSelectedListener(new Spinner.OnItemSelectedListener() {        @Override        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {            //選擇選項要做的事            switch (position){                case 0:                    mGender = "男生";                    break;                case 1:                    mGender = "";                    break;            }        }        @Override        public void onNothingSelected(AdapterView<?> parent) {            //沒有選擇選項要做的事        }    });`

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