Explore the principles and practice of Java quick sort

In-depth understanding of the principles and applications of Java Quick Sort

Quick Sort (Quick Sort) is a commonly used sorting algorithm. Its efficiency and advantages make it widely used Various programming languages, including Java. In this article, we will provide an in-depth understanding of the principles and applications of the Java quick sort algorithm and provide specific code examples.

1. Principle
The basic idea of ​​the quick sort algorithm is to continuously divide a large problem into small problems through the divide and conquer method, then sort the small problems, and finally merge the sorted results into a single sequence sequence.

Specifically, the implementation steps of the quick sort algorithm are as follows:

1. Select a pivot element (pivot), assuming it is the first element in the array.
2. Split the array into two sub-arrays, so that the elements in the first sub-array are less than or equal to the base element, and the elements in the second sub-array are greater than the base element. This process is called partition.
3. Apply the above steps recursively to the two subarrays until each subarray contains only one element, that is, the termination condition of the recursion is reached.
4. Combine the results of the sub-arrays to get the entire sorted array.

2. Application
The quick sort algorithm is widely used in practical applications, and its efficient sorting speed makes it a commonly used sorting algorithm. Below we demonstrate the application of quick sort through actual code examples.

public class QuickSort {
    public static void main(String[] args) {
        int[] arr = {10, 7, 8, 9, 1, 5};
        int n = arr.length;

        quickSort(arr, 0, n-1);

        System.out.println("排序后的数组：");
        for (int i : arr) {
            System.out.print(i + " ");
        }
    }

    public static void quickSort(int[] arr, int low, int high) {
        if (low < high) {
            int pi = partition(arr, low, high);

            // 对划分后的子数组进行递归排序
            quickSort(arr, low, pi-1);
            quickSort(arr, pi+1, high);
        }
    }

    public static int partition(int[] arr, int low, int high) {
        int pivot = arr[high];
        int i = (low-1);
        for (int j=low; j<high; j++) {
            if (arr[j] <= pivot) {
                i++;

                // 交换arr[i]和arr[j]
                int temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
            }
        }

        // 交换arr[i+1]和arr[high]
        int temp = arr[i+1];
        arr[i+1] = arr[high];
        arr[high] = temp;

        return i+1;
    }
}

The above code sorts the array through the quick sort algorithm and prints the sorted results. In this example, we select the last element in the array as the base element, divide the subarray by moving the smaller elements to the left of the base element, the larger elements to the right, and combine the results of the subarrays .

Through the above code and introduction, we can have a deeper understanding of the principles and applications of the Java quick sort algorithm. I hope this article will be helpful to readers and give everyone a more comprehensive understanding of the quick sort algorithm.

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