算法之二路归并排序

Posted 2020-10-13 纳木错星空

public class SortTest {
    private static int ARRAY_NUMBER=10;
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //准备待排序的序列
        Random random = new Random();
        int[] array = new int[ARRAY_NUMBER];
        for(int i = 0 ; i < array.length; i++){
            array[i] = random.nextInt(20);
        }
        System.out.println("数组的初始排序如下：\n");
        System.out.println(Arrays.toString(array));
        mergeSort(array,0,array.length-1);
        System.out.println("数组的归并排序后如下：\n");
        System.out.println(Arrays.toString(array));
    }
    //二路归并排序
    private static void mergeSort(int[] list,int left,int right){
        if(left < right){
            int mid = (left+right)/2;
            mergeSort(list,left,mid);
            mergeSort(list,mid+1,right);
            mergeration(list,left,mid,right);
        }
    }
    private static void mergeration(int[] list, int left, int mid, int right) {
        // TODO Auto-generated method stub
        int i,j,k;
        int[] temp = new int[right-left+1];
        k = 0;
        i=left;
        j=mid+1;
        while(i<=mid&&j<=right){
            if(list[i] <= list[j]){
                temp[k++] = list[i++];
            }else{
                temp[k++] = list[j++];
            }
        }
        while(i<=mid){
            temp[k++] = list[i++];
        }
        while(j<=right){
            temp[k++] = list[j++];
        }
        //排好序后复制回原来数组的相应分段中
        for(i=0;i<temp.length;i++){
            list[left+i]=temp[i];
        }
    }

}