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# 003  Squares of a Sorted Array

## Given an integer array `nums` sorted in **non-decreasing** order, return *an array of **the squares of each number** sorted in non-decreasing order*.

### **Example 1:**

```
Input: nums = [-4,-1,0,3,10]
Output: [0,1,9,16,100]
Explanation: After squaring, the array becomes [16,1,0,9,100].
After sorting, it becomes [0,1,9,16,100].
```

### **Example 2:**

```
Input: nums = [-7,-3,2,3,11]
Output: [4,9,9,49,121]
```

### **Constraints:**

* `1 <= nums.length <= 104`
* `-104 <= nums[i] <= 104`
* `nums` is sorted in **non-decreasing** order.

&#x20;**Follow up:** Squaring each element and sorting the new array is very trivial, could you find an `O(n)` solution using a different approach?

## Solution

### Code

{% tabs %}
{% tab title="C#" %}

```csharp
public class Solution {
	public int[] SortedSquares(int[] nums) {
		int[] squareNums = nums;
		int length= nums.Length;
        int temp;
		
		//Do square
		for(int i=0; i<length; i++){
			squareNums[i]=squareNums[i]*squareNums[i];
		}
        
        //Do sort in non-decreasing order ---- bubbleSort
        for(int j=0; j<length-1; j++){
            for(int k=0; k<length-1-j; k++){
                if(squareNums[k]>squareNums[k+1]){
                    temp = squareNums[k];
                    squareNums[k] = squareNums[k+1];
                    squareNums[k+1] =temp;
                }
            }
        }      
    return squareNums;
	}
}
```

{% endtab %}
{% endtabs %}

### Reference

#### 1、冒泡排序（Bubble Sort）

冒泡排序是一种简单的排序算法。它重复地走访过要排序的数列，一次比较两个元素，如果它们的顺序错误就把它们交换过来。走访数列的工作是重复地进行直到没有再需要交换，也就是说该数列已经排序完成。这个算法的名字由来是因为越小的元素会经由交换慢慢“浮”到数列的顶端。&#x20;

**1.1 算法描述**

* 比较相邻的元素。如果第一个比第二个大，就交换它们两个；
* 对每一对相邻元素作同样的工作，从开始第一对到结尾的最后一对，这样在最后的元素应该会是最大的数；
* 针对所有的元素重复以上的步骤，除了最后一个；
* 重复步骤1\~3，直到排序完成。

**1.2 代码实现**

```
function bubbleSort(arr) {
    var len = arr.length;
    for(var i = 0; i < len - 1; i++) {
        for(var j = 0; j < len - 1 - i; j++) {
            if(arr[j] > arr[j+1]) {        // Compare adjacent elements in pairs
                var temp = arr[j+1];        // Change elements
                arr[j+1] = arr[j];
                arr[j] = temp;
            }
        }
    }
    return arr;
}
```

**1.2 代码优化**

```
public static void sort(int arr[]){
    for( int i = 0;i < arr.length - 1 ; i++ ){
        boolean isSort = true;
        for( int j = 0;j < arr.length - 1 - i ; j++ ){
            int temp = 0;
            if(arr[j] < arr[j + 1]){
                temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
                isSort = false;
            }
        }
        if(isSort){
            break;
        }
    }
}
```

### More:

{% embed url="<https://www.cnblogs.com/onepixel/articles/7674659.html>" %}

{% embed url="<https://juejin.cn/post/6844903863288332302>" %}


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