这道题：是模拟出栈，判断出栈顺序的可能性。
基本上大家的做法都是直接模拟栈的出栈入栈并将顺序用0,1序列来表示，我暂时没想到什么好的思路。
import java.util.*;
import java.io.*;
public class Main{
public static void main(String[] arg){
Scanner scan = new Scanner(new BufferedInputStream(System.in));
int[] outFlag = new int[18];//最多有9辆火车，1表示出,0表示进
char[] stack = new char[20];
while(scan.hasNextInt()){
int n =scan.nextInt();
char[] put;
char[] pop;
put= scan.next().toCharArray();
pop = scan.next().toCharArray();
int top = -1;
int in=0,out=0,flag=0;
while(out!=n&&in!=n+1){
if(top!=-1&&stack[top] == pop[out]){
top--;
out++;
outFlag[flag++] = 1;
continue;
}
if(in==n){
break;
}
top++;
stack[top] = put[in++];
outFlag[flag++] = 0;
}
if(flag==2*n){
System.out.println("Yes.");
for(int i = 0 ; i!= flag ; i ++){
if(outFlag[i]==0){
System.out.println("in");
continue;
}
System.out.println("out");
}
}else{
System.out.println("No.");
}
System.out.println("FINISH");
}
scan.close();
}
}