快排

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荷兰国旗排序图示

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荷兰国旗排序code

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  int arr[] = {9, 8, 5, 7, 4, 9, 7, 5, 9, 8, 4, 2, 6, 5, 9, 1, 7, 5, 9,88,11};
    @Test
    public void quickSortTest(){
        quickSort(arr,0,arr.length-1);
        printArr();
    }
    public void quickSort(int[] arr, int l, int r) {
        if (l < r) {
            int[] p = partition(arr, l, r);
            quickSort(arr, l, p[0] - 1);
            quickSort(arr, p[1] + 1, r);
        }

    }
    private int[] partition(int[] arr, int l, int r) {
        int less = l - 1;
        int more = r ;
        while (l < more) {
            if (arr[l] < arr[r]) {//左边
                swap(++less, l++);
            } else if (arr[l] > arr[r]) {
                swap(--more, l);
            } else {
                l++;
            }
        }
        swap(more,r);
        int[] ints = {less + 1, more};//return index
        return ints;

    }

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    @Test
    public void test8() {
        String str = "aaafvjvnrjoooobbggggcc";
        boolean tag = false;
        char[] chars = str.toCharArray();
        StringBuilder sb = new StringBuilder();
        int len = chars.length - 1;
        for (int i = 0; i < len; i++) {
            if (i + 1 <= len && chars[i] == chars[i + 1]) {
                if (!tag) {
                    sb.append(chars[i]).append(chars[i + 1]);
                    tag = true;
                } else {
                    sb.append(chars[i]);
                }

            } else {
                if (tag && i < len - 1) {
                    sb.append(",");
                }
                tag = false;
            }
        }
        System.out.println("sb:--> " + sb.toString());
    }