题目描述
13计科的ppmm紫菱给她的追求者们出了道难题,现在有2n个1到9的整数为:2个“1”,2个“2”,….,2个”n”。看谁能用这2n个数字拼成一个数,满足2个“1”中间有1个数字,2个“2”中间有2个数字,…,2个“n”中间有n个数字。你能解出这题赢得紫菱的芳心吗?
输入
一个整数n, (1<=n<=9)
输出
按由小到大顺序输出满足条件的拼出来的数字,每个数字占一行
样例输入
3
样例输出
231213
312132
代码
import java.util.Scanner;
public class Main {
int n;
int[] A;
boolean[] Num;
boolean[] Mark;
public Main() {
Scanner sc = new Scanner(System.in);
n = sc.nextInt();
A = new int[2 * n];
Num = new boolean[n + 1];
Search(0);
}
void Search(int pos) {
if (pos == 2 * n) {
for (int k = 0; k < 2 * n; k++)
System.out.print(A[k]);
System.out.println();
return;
}
if (A[pos] != 0)
Search(pos + 1);
for (int i = 1; i <= n; i++) {
if (Num[i] == false && pos + i + 1 < 2 * n && A[pos] == 0 && A[pos + i + 1] == 0) {
A[pos] = i;
A[pos + i + 1] = i;
Num[i] = true;
Search(pos + 1);
A[pos] = 0;
A[pos + i + 1] = 0;
Num[i] = false;
}
}
}
public static void main(String[] args) {
Main p = new Main();
}
}