程序员必知的8大排序 （java）

以下是对应8种排序算法的示例代码（Java语言实现）：

1. 冒泡排序（Bubble Sort）：

public 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]) {
                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

2. 选择排序（Selection Sort）：

public 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;
            }
        }
        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

3. 插入排序（Insertion Sort）：

public 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

4. 快速排序（Quick Sort）：

public void quickSort(int[] arr, int low, int high) {
    if (low < high) {
        int pivotIndex = partition(arr, low, high);
        quickSort(arr, low, pivotIndex - 1);
        quickSort(arr, pivotIndex + 1, high);
    }
}

private 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++;
            int temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;
        }
    }
    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

5. 归并排序（Merge Sort）：

public 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 void merge(int[] arr, int low, int mid, int high) {
    int n1 = mid - low + 1;
    int n2 = high - mid;
    int[] leftArr = new int[n1];
    int[] rightArr = new int[n2];
    for (int i = 0; i < n1; i++) {
        leftArr[i] = arr[low + i];
    }
    for (int j = 0; j < n2; j++) {
        rightArr[j] = arr[mid + 1 + j];
    }
    int i = 0, j = 0, k = low;
    while (i < n1 && j < n2) {
        if (leftArr[i] <= rightArr[j]) {
            arr[k] = leftArr[i];
            i++;
        } else {
            arr[k] = rightArr[j];
            j++;
        }
        k++;
    }
    while (i < n1) {
        arr[k] = leftArr[i];
        i++;
        k++;
    }
    while (j < n2) {
        arr[k] = rightArr[j];
        j++;
        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
36
37
38
39
40
41
42

6. 堆排序（Heap Sort）：

public void heapSort(int[] arr) {
    int n = arr.length;
    for (int i = n / 2 - 1; i >= 0; i--) {
        heapify(arr, n, i);
    }
    for (int i = n - 1; i >= 0; i--) {
        int temp = arr[0];
        arr[0] = arr[i];
        arr[i] = temp;
        heapify(arr, i, 0);
    }
}

private void heapify(int[] arr, int n, int rootIndex) {
    int largest = rootIndex;
    int leftChild = 2 * rootIndex + 1;
    int rightChild = 2 * rootIndex + 2;
    if (leftChild < n && arr[leftChild] > arr[largest]) {
        largest = leftChild;
    }
    if (rightChild < n && arr[rightChild] > arr[largest]) {
        largest = rightChild;
    }
    if (largest != rootIndex) {
        int temp = arr[rootIndex];
        arr[rootIndex] = arr[largest];
        arr[largest] = temp;
        heapify(arr, n, largest);
    }
}
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

7. 希尔排序（Shell Sort）：

public void shellSort(int[] arr) {
    int n = arr.length;
    for (int gap = n / 2; gap > 0; gap /= 2) {
        for (int i = gap; i < n; i++) {
            int temp = arr[i];
            int j = i;
            while (j >= gap && arr[j - gap] > temp) {
                arr[j] = arr[j - gap];
                j -= gap;
            }
            arr[j] = temp;
        }
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14

8. 计数排序（Counting Sort）：

public void countingSort(int[] arr) {
    int n = arr.length;
    int max = Arrays.stream(arr).max().getAsInt();
    int min = Arrays.stream(arr).min().getAsInt();
    int range = max - min + 1;
    int[] count = new int[range];
    int[] output = new int[n];
    for (int i = 0; i < n; i++) {
        count[arr[i] - min]++;
    }
    for (int i = 1; i < range; i++) {
        count[i] += count[i - 1];
    }
    for (int i = n - 1; i >= 0; i--) {
        output[count[arr[i] - min] - 1] = arr[i];
        count[arr[i] - min]--;
    }
    for (int i = 0; i < n; i++) {
        arr[i] = output[i];
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21