数组后面的Java插入排序算法

Question

So I have been trying to write the insertion sort algorithm so that the values are inserted towards the back of the array rather than the front (putting the largest values towards the back rather than the smallest towards the front) and I have been having trouble seeing if I am doing it right. If someone can tell me if I have the right idea, that'd be great. Here is my code, it doesn't seem to work as I want it to:

public static void insertionSort(Comparable[] item, int size) {
    for (int k = size - 1; k > 0; k--)
        insertInOrder(item, k);
}

private static void insertInOrder(Comparable[] item, int m) {
    Comparable save = item[m];
    for (; m > 0 && item[m-1].compareTo(save) > 0; m--)
        item[m] = item[m - 1];
    item[m] = save;
}

Answer 1

There are two problems with your code. Here is a fixed version:

public static void insertionSort(Comparable[] item, int size) {
    // Changed to k >= 0, otherwise we would have ignored the 0th
    // element and not move it to higher positions in the array
    for (int k = size - 1; k >= 0; k--)
        insertInOrder(item, k, size);
}

// Added size as a parameter
private static void insertInOrder(Comparable[] item, int m, int size) {
    Comparable save = item[m];
    // This loop needs to count upward, because you
    // want to move large values towards the back
    for (; m + 1 < size && item[m+1].compareTo(save) < 0; m++)
        item[m] = item[m + 1];
    item[m] = save;
}

---

Additional notes:

• Normally we pluralize the name of an array, ie: Comparable[] items .
• Consider using generics for the Comparable type.
• Ask your question next time on Code Review Stack Exchange .