Question

我可以使用Java Assignment的一些帮助，我要写一个插入排序和快速排序来对对象的arraylist进行排序，并发现自己陷入困境。排序似乎没有给出我期望的输出，即。将元素按字母顺序排序。

- 插入排序 - 空客A380，泰坦尼克号， BOXTER，协和广场，空客A380

- 快速排序 - 恩佐，泰坦尼克号，协和广场， BOXTER，空客A380

以上是我得到的输出。

protected ArrayList<Vehicle> insertionSort(ArrayList<Vehicle> list)
{

    ArrayList<Vehicle> sorted = new ArrayList<Vehicle>(list);

    int n = list.size();
    for (int j = 1; j < n; j++)
    {
        Vehicle key = list.get(j);
        Vehicle pivot = list.get(j-1);
        int i = j-1;

        for(i = j - 1; (i >= 0) && (pivot.compareTo(key)) > 0; i--)   // Smaller values are moving down
        {
            sorted.set(i, list.get(i));
        }
        sorted.set(i+1, key);    // Put the key in its proper location

    }

    return sorted;
}


protected ArrayList<Vehicle> quickSort(ArrayList<Vehicle> list, int low, int high)
{


    ArrayList<Vehicle> sorted = new ArrayList<Vehicle>(list);

    int i = low; int j = high;
    // Get the pivot element from the middle of the list
    Vehicle pivot = list.get(low + (high - low) / 2);

    // Divide into two lists
    while (i <= j) {
        // If the current value from the left list is smaller then the pivot
        // element then get the next element from the left list
        while (list.get(i).compareTo(pivot) > 0 )
        {
            i++;
        }
        // If the current value from the right list is larger then the pivot
        // element then get the next element from the right list
        while (list.get(j).compareTo(pivot) < 0 )  
        {
            j--;
        }

        // If we have found a value in the left list which is larger than
        // the pivot element and if we have found a value in the right list
        // which is smaller then the pivot element then we exchange the
        // values.
        // As we are done we can increase i and j
        if (i <= j) {
            sorted.set(i,list.get(j));
            sorted.set(j,list.get(i));
            i++;
            j--;
        }
    }

    if (low < j)
        quickSort(sorted, low, j);
    if (i < high)
        quickSort(sorted, i, high);

    return sorted;
}

Answer 1

尝试对快速排序代码进行以下修复：

        while (list.get(i).compareTo(pivot) < 0 )   // < (not >)
        // ...
        while (list.get(j).compareTo(pivot) > 0 )   // > (not <)

插入＆amp;快速排序对象的数组列表

1 个答案: