Question

因此代码的基本整体功能是接收数组并按升序排序。我的代码中没有错误，但我认为有些错误。我做了一些测试用例，有些已经失败了，我感觉recursivesort方法我做错了。我已经完成了多次调试，无法找到问题所在？

public class RecursiveSorter {

    private int[] sortedArray;
    private int[] array;

    public RecursiveSorter() {
        array = new int[1];
    }

    public RecursiveSorter(int[] a) {
        array = a;
    }

    public void setArray(int[] a) {
        array = a;
    }

    public int[] getSortedArray() {
        return sortedArray;
    }

    public int[] getOriginalArray() {
        return array;
    }

    public int[] sort() {
        sortedArray = array;
        recursiveSort(sortedArray.length - 1); 
        return sortedArray;
    }

    public int[] recursiveSort(int endIndex) {
        if (endIndex >= 0) {
            int m = getMaxIndex(endIndex, sortedArray);
            swap(m, endIndex, sortedArray);
            recursiveSort(endIndex-1);
        }
        return sortedArray;
    }

    public int getMaxIndex(int endIndex, int[] a) {
        int max = a[0];
        int maxIndex = 0;
        for (int i = 1; i < endIndex; i++) {
            if (a[i] > max) {  
                max = a[i];
                maxIndex = i;
            }
        }
        return maxIndex;
    }

    public void swap(int src, int dest, int[] a) {
        int temp = a[dest];
        a[dest] = src;
        a[src] = temp;
    }

    public String toString() {
        return "Original: " + prettyPrint(getOriginalArray()) + "\n" +
               "Sorted:   " + prettyPrint(getSortedArray());
    }

    private String prettyPrint(int[] a) {
        String s = "";
        for (int i : a)
            s += i + " ";
        return s;
    }

    public static void main(String[] args) {
        // Automate running, but not testing
        int[] array = {5, 67, 12, 20};
        RecursiveSorter s = new RecursiveSorter(array);
        s.sort();
        System.out.println(s); // uses Sorter.toString
    }
}

Answer 1

交换方法有错误：

a[dest] = src;

应该是：

a[dest] = a[src];

此行也不会复制数组，因此array和sortedArray引用相同的数组对象。

sortedArray = array;

将其替换为：

sortedArray = Arrays.copyOf(array, array.length);

同样在方法getMaxIndex中缺少等号：

for (int i = 1; i < endIndex; i++) {

应该是：

for (int i = 1; i <= endIndex; i++) {

Answer 2

1 - 您必须将数组克隆（或复制）到sortedArray。

2 - 交换方法不正确。

3 - 方法recursiveSort的第一次调用应该由数组的最后一个索引进行参数化，使得sortedArray.length - 1。

public class RecursiveSorter {

    private int[] sortedArray;
    private int[] array;

    public RecursiveSorter() {
        array = new int[1];
    }

    public RecursiveSorter(int[] a) {
        array = a;
    }

    public void setArray(int[] a) {
        array = a;
    }

    public int[] getSortedArray() {
        return sortedArray;
    }

    public int[] getOriginalArray() {
        return array;
    }

    public void sort() {
        sortedArray = array.clone();
        System.out.println(this);
        recursiveSort(sortedArray.length - 1); //Should subtract by length
    }

    public void recursiveSort(int endIndex) {
        System.out.println("Sorting with param : "+endIndex);
        if (endIndex >= 0) {
            int m = getMaxIndex(endIndex, sortedArray);
            swap(m, endIndex);
            System.out.println(this);
            recursiveSort(endIndex - 1);
        }
    }

    public int getMaxIndex(int endIndex, int[] a) {
        int max = a[0];
        int maxIndex = 0;
        for (int i = 1; i <= endIndex; i++) {
            if (a[i] > max) {
                max = a[i];
                maxIndex = i;
                System.out.println("Max index : " + i);
            }
        }
        return maxIndex;
    }

    public void swap(int src, int dest) {
        System.out.println("Swap : "+src+" to "+dest);
        int temp = sortedArray[dest];
        sortedArray[dest] = sortedArray[src];
        sortedArray[src] = temp;
    }

    public String toString() {
        return "Original: " + prettyPrint(getOriginalArray()) + "\n"
                + "Sorted:   " + prettyPrint(getSortedArray());
    }

    private String prettyPrint(int[] a) {
        String s = "";
        for (int i : a) {
            s += i + " ";
        }
        return s;
    }

    public static void main(String[] args) {
        // Automate running, but not testing
        int[] array = {5, 67, 12, 20};
        RecursiveSorter s = new RecursiveSorter(array);
        s.sort();
        //System.out.println(s); // uses Sorter.toString
    }
}

遇到方法功能问题

2 个答案: