手写java冒泡、插入、选择、快速、归并排序算法

Java中有许多种不同的排序算法，下面是一些常见的排序算法的实现示例：

1. 冒泡排序(Bubble Sort)

public static void bubbleSort(int[] arr) {
    int n = arr.length;
    for (int i = 0; i < n-1; i++) {
        for (int j = 0; j < n-i-1; j++) {
            if (arr[j] > arr[j+1]) {
                // 交换arr[j]和arr[j+1]
                int temp = arr[j];
                arr[j] = arr[j+1];
                arr[j+1] = temp;
            }
        }
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13

2. 插入排序(Insertion Sort)

public static void insertionSort(int[] arr) {
    int n = arr.length;
    for (int i = 1; i < n; i++) {
        int key = arr[i];
        int j = i-1;
        while (j >= 0 && arr[j] > key) {
            arr[j+1] = arr[j];
            j--;
        }
        arr[j+1] = key;
    }
}
1
2
3
4
5
6
7
8
9
10
11
12

3. 选择排序(Selection Sort)

public static void selectionSort(int[] arr) {
    int n = arr.length;
    for (int i = 0; i < n-1; i++) {
        int minIndex = i;
        for (int j = i+1; j < n; j++) {
            if (arr[j] < arr[minIndex]) {
                minIndex = j;
            }
        }
        // 交换arr[i]和arr[minIndex]
        int temp = arr[i];
        arr[i] = arr[minIndex];
        arr[minIndex] = temp;
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

4. 快速排序(Quick Sort)

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);
    }
}

private 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;
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26

5. 归并排序(Merge Sort)

public static void mergeSort(int[] arr, int low, int high) {
    if (low < high) {
        int mid = (low + high) / 2;
        mergeSort(arr, low, mid);
        mergeSort(arr, mid+1, high);
        merge(arr, low, mid, high);
    }
}

private static void merge(int[] arr, int low, int mid, int high) {
    int[] temp = new int[arr.length];
    for (int i = low; i <= high; i++) {
        temp[i] = arr[i];
    }

    int i = low;
    int j = mid+1;
    int k = low;
    while (i <= mid && j <= high) {
        if (temp[i] <= temp[j]) {
            arr[k] = temp[i];
            i++;
        } else {
            arr[k] = temp[j];
            j++;
        }
        k++;
    }

    while (i <= mid) {
        arr[k] = temp[i];
        i++;
        k++;
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35

这里只给出了一种实现方式，实际上这些算法还有很多不同的变体和优化方法。