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();
}
}
