MergeSort在我的代码中不起作用

Question

我尝试实现MergeSort，但它没有显示数字的正确顺序。我想看看我的代码中发生了什么以及如何正确地修复它。

public class MergeSort {

    private static void sort(int[]a,int start,int end){
        if(start>=end){return;}

        int halfway=(start+end)/2;
        sort(a,start,halfway);
        sort(a,halfway+1,end);
        //now that the halves are sorted
        int []scratch=new int[end-start+1];
        int g1=start,g2=halfway+1;//i is the next inedex in the first half to consider
        //j is the next index in the second half to consder
        //k is the next index to populating in the scrach arry
        for(int p=0;p<=scratch.length;p++){


            if(a[g1]<a[g2]){
                scratch[p]=a[g1];g1++;//smaller one is a[i]
                if(g1>=halfway){break;}

            }


            else {scratch[p]=a[g2];
                g2++;
                if (g2>=end){break;}
            }
            if(g1>halfway+1){
                scratch[p]=a[g2];
                    g2++;
                }
            if(g2>end+1){
                scratch[p]=a[g1];
                g1++;
            }
            scratch=a;


        }

    }
    public static void sort(int[]a)
            {
        sort(a,0,a.length-1);

            }
    public static void main(String[] args){
        int[] starter={2,1,3,5,6,7,8};
        sort( starter);
        for(int i=0;i<starter.length;i++){
            System.out.print(" "+starter[i]);
        }

    }
}
//if first stack is empty then you grab the next one,
//if get1 pass to the stopat1(mid+1），then it need to copy the rest of the number,the rest of number are being sorted
//It also apply at get2 as well.

Answer 1

您可以阅读java.util.Collections.sort（starter）;

public static <T extends Comparable<? super T>> void sort(List<T> list) {
    Object[] a = list.toArray();
    Arrays.sort(a);
    ListIterator<T> i = list.listIterator();
    for (int j=0; j<a.length; j++) {
        i.next();
        i.set((T)a[j]);
    }
}