跪求,裸求.大神正解.一到十,十个数.解决思路

public class Traversal {    static long thesum = 0;    public static void main(String[] args) {        int buf[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};        perm(buf, 0, buf.length - 1);        System.out.println("thesum is :" + thesum);    }    public static void perm(int[] buf, int start, int end) {        if (start == end) {//当只要求对数组中一个字母进行全排列时，只要就按该数组输出即可              for (int i = 1; i <= end; i++) {                if (((buf[i] - buf[i - 1]) == 1) || ((buf[i] - buf[i - 1]) == -1)) {                     return;                }            }            System.out.print("_" + thesum + " ");            for (int i = 0; i <= end; i++) {                System.out.print(buf[i]);            }            thesum++;            System.out.println();        } else {//多个字母全排列              for (int i = start; i <= end; i++) {                int temp = buf[start];//交换数组第一个元素与后续的元素                  buf[start] = buf[i];                buf[i] = temp;                perm(buf, start + 1, end);//后续元素递归全排列                  temp = buf[start];//将交换后的数组还原                  buf[start] = buf[i];                buf[i] = temp;            }        }    }}