冒泡排序快速排序选择排序（Java实现）

Posted 2022-12-09 听风者-better

1.冒泡排序

package sort;

public class BubbleSort 
	public static void main(String[] args) 
		int[] arr = new int[]  2, 6, 1, 3, 9, 34, 27, 18, 28, 87, 73, 90 ;
		System.out.println("排序前");
		for (int num : arr) 
			System.out.print(num + " ");
		
		sort(arr);
		System.out.println();
		System.out.println("排序后");
		for (int num : arr) 
			System.out.print(num + " ");
		
	

	public static void sort(int[] arr) 
		for (int i = 0; i < arr.length - 1; i++) 
			for (int j = 0; j < arr.length - 1 - i; i++) 
				if (arr[j] > arr[j + 1]) 
					int temp = arr[j];
					arr[j] = arr[j + 1];
					arr[j + 1] = temp;
				
			
		
	

2.选择排序

package sort;

public class SelectSort 
	public static void main(String[] args) 
		int[] arr = new int[]  2, 6, 1, 3, 9, 34, 27, 18, 28, 87, 90, 77 ;
		System.out.println("排序前");
		for (int num : arr) 
			System.out.print(num + " ");
		
		sort(arr);
		System.out.println();
		System.out.println("排序后");
		for (int num : arr) 
			System.out.print(num + " ");
		
	

	public static void sort(int[] arr) 
		for (int i = 0; i < arr.length - 1; i++) // 做第i趟排序
			int index = i;// 选最小的记录
			for (int j = index + 1; j < arr.length; j++) 
				if (arr[index] > arr[j]) 
					index = j;// 记下目前找到的最小值所在的位置
				
			
			// 在内层循环结束，也就是找到本轮循环的最小的数以后，再进行交换
			if (index != i) 
				int temp = arr[i];
				arr[i] = arr[index];
				arr[index] = temp;
			
		
	

3.快速排序

参考文章：https://blog.csdn.net/shujuelin/article/details/82423852

package sort;

public class QuickSort 
	public static void main(String[] args) 
		int[] arr =  2, 6, 1, 3, 9, 34, 27, 18, 28, 87, 73, 90 ;
		System.out.println("排序前数组为：");
		for (int num : arr) 
			System.out.print(num + " ");
		
		int start = 0;
		int end = arr.length - 1;
		sort(arr, start, end);
		System.out.println();
		System.out.println("排序后的数组为：");
		for (int num : arr) 
			System.out.print(num + " ");
		
	

	private static int getMiddle(int[] arr, int start, int end) 
		int i = start;
		int j = end;
		int key = arr[start];
		while (i < j) 
			while (i < j && arr[j] >= key) 
				j--;
			
			while (i < j && arr[i] <= key) 
				i++;
			
			if (i < j) 
				int temp = arr[i];
				arr[i] = arr[j];
				arr[j] = temp;
			
		
		arr[start] = arr[i];
		arr[i] = key;
		return i;
	

	private static void sort(int[] arr, int start, int end) 
		if (start < end) 
			int index = getMiddle(arr, start, end);
			sort(arr, start, index - 1);
			sort(arr, index + 1, end);