（HDU - 1022）Train Problem I

（HDU - 1022）Train Problem I

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)

Total Submission(s): 39116 Accepted Submission(s): 14717

Problem Description

As the new term comes, the Ignatius Train Station is very busy nowadays. A lot of student want to get back to school by train(because the trains in the Ignatius Train Station is the fastest all over the world ^v^). But here comes a problem, there is only one railway where all the trains stop. So all the trains come in from one side and get out from the other side. For this problem, if train A gets into the railway first, and then train B gets into the railway before train A leaves, train A can’t leave until train B leaves. The pictures below figure out the problem. Now the problem for you is, there are at most 9 trains in the station, all the trains has an ID(numbered from 1 to n), the trains get into the railway in an order O1, your task is to determine whether the trains can get out in an order O2.

Input

The input contains several test cases. Each test case consists of an integer, the number of trains, and two strings, the order of the trains come in:O1, and the order of the trains leave:O2. The input is terminated by the end of file. More details in the Sample Input.

Output

The output contains a string “No.” if you can’t exchange O2 to O1, or you should output a line contains “Yes.”, and then output your way in exchanging the order(you should output “in” for a train getting into the railway, and “out” for a train getting out of the railway). Print a line contains “FINISH” after each test case. More details in the Sample Output.

Sample Input

3 123 321
3 123 312

Sample Output

Yes.
in
in
in
out
out
out
FINISH
No.
FINISH

Hint

For the first Sample Input, we let train 1 get in, then train 2 and train 3.
So now train 3 is at the top of the railway, so train 3 can leave first, then train 2 and train 1.
In the second Sample input, we should let train 3 leave first, so we have to let train 1 get in, then train 2 and train 3.
Now we can let train 3 leave.
But after that we can’t let train 1 leave before train 2, because train 2 is at the top of the railway at the moment.
So we output “No.”.

题目大意：有一个火车站类似于栈（满足先进后出），给出两个序列s1,s2分别为火车进站出站的顺序，问是否这两个序列是否满足题意。

思路：用栈模拟火车进出站，匹配输出序列，若栈顶与输出相同就出栈，记录下进出站的顺序，若比较到末尾则说明可行，否则不行。

#include<cstdio>
#include<stack>
#include<cstring>
using namespace std;

const int maxn=100005;
char s1[maxn],s2[maxn];
int in[maxn];//记录火车是出站还是进站，进站1，出站0 

int main()
{
    int n;
    while(~scanf("%d%s%s",&n,s1,s2))
    {
        memset(in,-1,sizeof(in));
        stack<char> st;
        st.push(s1[0]);
        in[0]=1;
        int i=0,j=0,tot=1;
        while(i<n&&j<n)
        {
            if(!st.empty()&&st.top()==s2[j])
            {
                j++;
                st.pop();
                in[tot++]=0;
            }
            else
            {
                i++;
                if(i==n) break;//说明没有全部元素出栈，不满足要求 
                st.push(s1[i]);
                in[tot++]=1;
            }
        }
        if(i==n) printf("No.\n");
        else
        {
            printf("Yes.\n");
            for(int i=0;i<tot;i++)
            {
                if(in[i]==1) printf("in\n");
                if(in[i]==0) printf("out\n");
            }
        } 
        printf("FINISH\n");
    }
    return 0;
}