Key tips and precautions for mastering Java quick sort
Quick Sort (Quick Sort) is a commonly used sorting algorithm. Its core idea is to select a benchmark elements, divide the sequence to be sorted into two independent parts, one part has all elements smaller than the reference element, and the other part has all elements greater than the reference element, and then recursively sorts the two parts to finally get the ordered sequence.
Although the time complexity of quick sort is O(nlogn) in the average case, it will degenerate to O(n^2) in the worst case, so in actual use, we need to master some keys Tips and considerations to make quick sort more efficient.
The following is a sample code to demonstrate how to implement quick sort:
public class QuickSort { public static void quickSort(int[] arr, int low, int high) { if (low < high) { int pivot = partition(arr, low, high); quickSort(arr, low, pivot - 1); quickSort(arr, pivot + 1, high); } } public static int partition(int[] arr, int low, int high) { int pivot = arr[low]; while (low < high) { while (low < high && arr[high] >= pivot) { high--; } arr[low] = arr[high]; while (low < high && arr[low] <= pivot) { low++; } arr[high] = arr[low]; } arr[low] = pivot; return low; } public static void main(String[] args) { int[] arr = {5, 3, 2, 1, 4}; quickSort(arr, 0, arr.length - 1); for (int num : arr) { System.out.print(num + " "); } } }
In the above code, we define the quickSort
method to complete quick sorting Sort. Inside the method, we first select the first element of the sequence to be sorted as the base element, and divide it by calling the partition
method. The partition
method uses double pointers, starting from both ends of the sequence, moving the pointers toward the middle until they meet, and swapping the positions of elements smaller than the base element and elements larger than the base element. Finally, insert the base element where it meets.
In the main
method, we tested the quick sort algorithm. The output result is 1 2 3 4 5
, indicating that the sorting is correct.
By mastering the above key skills and precautions, we can better understand and apply the quick sort algorithm, thereby improving the efficiency and accuracy of sorting. At the same time, in actual development, we can further optimize the algorithm, such as using the three-number method to select benchmark elements to avoid the worst case scenario. In short, quick sort is a very practical and efficient sorting algorithm that is worth mastering and in-depth study.
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