排序

public class sort {
    public static void main(String[] args) {
        int[] init = {0, 0, 0, -1, -1, 4, -7, 8, 10, 10, 3, -2, 1345, -2345,};
//        Arrays.stream(bubbleSort(init)).forEach(System.out::println);
//        Arrays.stream(insertSort(init)).forEach(System.out::println);
//        Arrays.stream(quickSort(init,0,init.length-1)).forEach(System.out::println);
//        mergeSort(init, 0, init.length - 1);
//        Arrays.stream(init).forEach(System.out::println);
    }

    /**
     * 冒泡排序
     * @param arr
     * @return
     */
    public static int[] bubbleSort(int[] arr) {
        for (int i = 0; i < arr.length - 1; i++) {
            for (int j = 0; j < arr.length - 1 - i; j++) {
                if (arr[j] > arr[j + 1]) {
                    int temp = arr[j];
                    arr[j] = arr[j + 1];
                    arr[j + 1] = temp;
                }
            }
        }
        return arr;
    }

    /**
     * 插入排序
     * @param arr
     * @return
     */
    public static int[] insertSort(int[] arr) {
        for (int i = 1; i < arr.length; i++) {
            int insertVal = arr[i];
            int index = i - 1;
            while (index >= 0 && insertVal <= arr[index]) {
                arr[index + 1] = arr[index];
                index--;
            }
            arr[index + 1] = insertVal;
        }
        return arr;
    }

    /**
     * 快速排序
     * @param arr
     * @param low
     * @param high
     * @return
     */
    public static int[] quickSort(int[] arr, int low, int high) {
        int start = low;
        int end = high;
        int key = arr[start];
        while (end > start) {
            while (end > start && arr[end] >= key) {
                end--;
            }
            if (arr[end] <= key) {
                int temp = arr[end];
                arr[end] = arr[start];
                arr[start] = temp;
            }
            while (end > start && arr[start] <= key) {
                start++;
            }
            if (arr[start] >= key) {
                int temp = arr[start];
                arr[start] = arr[end];
                arr[end] = temp;
            }
        }
        if (start > low) quickSort(arr, low, start - 1);
        if (end < high) quickSort(arr, end + 1, high);
        return arr;
    }

    /**
     * 归并排序
     * @param arr
     * @param left
     * @param right
     */
    public static void mergeSort(int[] arr, int left, int right) {
        if (left >= right) {
            return;
        }
        int mid = left + (right-left) / 2;
        mergeSort(arr, left, mid);
        mergeSort(arr, mid + 1, right);
        toMerge(arr, left, mid, right);
    }

    private static void toMerge(int[] arr, int left, int mid, int right) {
        int temp[] = new int[arr.length];
        int thirdRight = mid + 1;
        int thirdLeft = left;

        int tmp = left;

        while (left <= mid && thirdRight <= right) {
            if (arr[left] <= arr[thirdRight]) {
                temp[thirdLeft++] = arr[left++];
            } else {
                temp[thirdLeft++] = arr[thirdRight++];
            }
        }

        while (thirdRight <= right) {
            temp[thirdLeft++] = arr[thirdRight++];
        }
        while (left <= mid) {
            temp[thirdLeft++] = arr[left++];
        }

        while (tmp <= right) {
            arr[tmp] = temp[tmp++];
        }
    }
}