Question

我在java中编写合并排序类，当我到达sort(left)行时，我收到堆栈溢出错误。有什么想法吗？我不明白为什么这会是一个问题。

包ds;

import java.util.Comparator;

public class MergeSorter<T> extends Sorter<T> {

public MergeSorter(Comparator<T> comparator){
    super(comparator);
}

@SuppressWarnings("unchecked")
@Override
public void sort(T[] array){
    if (array.length <= 1);
    else {
        T[] left = (T[]) new Object[array.length/2 + 1];
        T[] right = (T[]) new Object[array.length/2 + 1];
        int middleIndex = array.length / 2;
        for (int i = 0; i < middleIndex; i++) {
            left[i] = array[i];
        }
        for (int i = middleIndex; i < array.length; i++) {
            right[i - middleIndex] = array[i];
        }
        sort(left);
        sort (right);
        merge(left, right, array);
    }
}

public final void merge(T[] left, T[] right, T[] array){
    Array<T> sortedArray = new Array<T>(array.length);
    while (left.length > 0 || right.length > 0) {
        if (left.length > 0 && right.length > 0) {
            if (comparator.compare(left[0], right[0]) < 0) {
                sortedArray.add(left[0]);
                for (int i = 1; i < left.length; i++) {
                    left[i - 1] = left[i];
                    left[left.length - 1] = null;
                }
            }
            else {
                sortedArray.add(right[0]);
                for (int i = 1; i < right.length; i++) {
                    right[i - 1] = right[i];
                    right[right.length - 1] = null;
                }
            }
        }
        else if (left.length > 0) {
            sortedArray.add(left[0]);
            for (int i = 1; i < left.length; i++) {
                left[i - 1] = left[i];
                left[left.length - 1] = null;
            }
        }
        else if (right.length > 0) {
            sortedArray.add(right[0]);
            for (int i = 1; i < right.length; i++) {
                right[i - 1] = right[i];
                right[right.length - 1] = null;
            }
        }
    }
    for (int i = 0; i < array.length; i++) {
        array[i] = sortedArray.get(i);
    }
}

}

Answer 1

假设数组的长度为2。然后左边是：

T[] left = (T[]) new Object[array.length/2 + 1];

是

T[] left = (T[]) new Object[2/2 + 1];

，这相当于

T[] left = (T[]) new Object[2];

当您对left进行排序时，这会继续，并导致无限递归，这可能导致您发布的堆栈溢出错误。

由于您要将第一个middleIndex元素复制到left，因此middleIndex长度应该适合数组left。因此left应该是长度为array.length/2的数组。

合并排序算法中的堆栈溢出错误？

1 个答案: