Java 【数据结构】常见排序算法实用详解 插入排序/希尔排序/选择排序/堆排序

以下是插入排序、希尔排序、选择排序和堆排序的Java实现示例代码：

// 插入排序
public void insertionSort(int[] arr) {
    for (int i = 1; i < arr.length; i++) {
        int key = arr[i];
        int j = i - 1;
 
        // 移动元素
        while (j >= 0 && arr[j] > key) {
            arr[j + 1] = arr[j];
            j = j - 1;
        }
        arr[j + 1] = key;
    }
}
 
// 希尔排序
public void shellSort(int[] arr) {
    int n = arr.length;
    int h = 1;
    while (h < n / 3) {
        h = h * 3 + 1;
    }
 
    while (h >= 1) {
        for (int i = h; i < n; i++) {
            int temp = arr[i];
            int j = i;
            while (j >= h && arr[j - h] > temp) {
                arr[j] = arr[j - h];
                j = j - h;
            }
            arr[j] = temp;
        }
        h = h / 3;
    }
}
 
// 选择排序
public void selectionSort(int[] arr) {
    for (int i = 0; i < arr.length - 1; i++) {
        int minIndex = i;
        for (int j = i + 1; j < arr.length; j++) {
            if (arr[j] < arr[minIndex]) {
                minIndex = j;
            }
        }
        int temp = arr[minIndex];
        arr[minIndex] = arr[i];
        arr[i] = temp;
    }
}
 
// 堆排序
public void heapSort(int[] arr) {
    int n = arr.length;
 
    // Build heap (rearrange array)
    for (int i = n / 2 - 1; i >= 0; i--) {
        heapify(arr, n, i);
    }
 
    // One by one extract elements
    for (int i = n - 1; i >= 0; i--) {
        // Move current root to end
        int temp = arr[0];
        arr[0] = arr[i];
        arr[i] = temp;
 
        // heapify the root element
        heapify(arr, i, 0);
    }
}
 
private void heapify(int[] arr, int n, int i) {
    int largest = i; // Initialize largest as root
    int l = 2 * i + 1; // left = 2*i + 1
    int r = 2 * i + 2; // right = 2*i + 2
 
    // If left child is larger than root
    if (l < n && arr[l] > arr[largest]) {
        largest = l;
    }
 
    // If right child is larger than largest so far
    if (r < n && arr[r] > arr[largest]) {
        largest = r;
    }
 
    // If largest is not root
    if (largest != i) {
        int swap = arr[i];
        arr[i] = arr[largest];
        arr[largest] = swap;
 
        // Recursively heapify the affected sub-tree
        heapify(arr, n, largest);
    }
}