java - 执行堆排序时出现错误

Question

我正在尝试在 Java 中使用此数组创建堆并对其进行排序。我不断得到

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 42
at HeapSort.exchange(HeapSort.java:28)
at HeapSort.Max_Heapify(HeapSort.java:22)
at HeapSort.Build_Heap at HeapSort.Sort(HeapSort.java:36)
at HeapSort.main(HeapSort.java:46)

我不确定错误从何而来。

public class HeapSort {
    public static int n;
    public static int[] a;
    public static int largest;

    public static void Build_Heap(int[] a){
        n = a.length-1;
        for(int i = n/2; i >= 0; i--){
            Max_Heapify(a,i);
        }
    }
    public static void Max_Heapify(int[] a,int i){
        int left = 2*i;
        int right = 2*i +1;

        if(left <= n && a[left] > a[i])
            largest = left;
        if(right <=n && a[right] > a[largest])
            largest = right;
        if(largest != i)
            exchange (a[i],a[largest]);
        Max_Heapify(a,largest);
    }


    private static void exchange(int i, int j) {
        int temp = a[i];
        a[i] = a[j];
        a[j] = temp;
        // TODO Auto-generated method stub

    }
    public static void Sort(int[] a0){
        a = a0;
        Build_Heap(a);

        for(int i = n; i > 0; i--){
            exchange(0,i);
            n = n-1;
            Max_Heapify(a,0);
        }
    }
    public static void main(String[] args){
        int[] a1 = {3,55,6,42,34,56,34};
        Sort(a1);
        for(int i = 0; i < a1.length; i++){
            System.out.print(a1[i] + " ");
        }
    }
}

Answer 1

您在 exchange() 中遇到错误。该方法的参数 i 和 j 看起来像是数组 a 的索引。但是，您正在调用方法 exchange(a[i],a[largest]) ，该方法正在传递数组中索引 i 和 largest 处的值 而不是将实际索引 i 和 largest 传递给该方法。

尝试像 exchange(i,largest) 那样调用交换