Problem Description

A stack is a data structure in which all insertions and deletions of entries are made at one end, called the "top" of the stack. The last entry which is inserted is the first one that will be removed. In another word, the operations perform in a Last-In-First-Out
(LIFO) manner.
A mergeable stack is a stack with "merge" operation. There are three kinds of operation as follows:

- push A x: insert x into stack A
- pop A: remove the top element of stack A
- merge A B: merge stack A and B

After an operation "merge A B", stack A will obtain all elements that A and B contained before, and B will become empty. The elements in the new stack are rearranged according to the time when they were pushed, just like repeating their "push" operations in
one stack. See the sample input/output for further explanation.
Given two mergeable stacks A and B, implement operations mentioned above.

 

Input

There are multiple test cases. For each case, the first line contains an integer N(0<N≤105),
indicating the number of operations. The next N lines, each contain an instruction "push", "pop" or "merge". The elements of stacks are 32-bit integers. Both A and B are empty initially, and it is guaranteed that "pop" operation would not be performed to an
empty stack. N = 0 indicates the end of input.

 

Output

For each case, print a line "Case #t:", where t is the case number (starting from 1). For each "pop" operation, output the element that is popped, in a single line.

 

Sample Input

 

Sample Output

 

Author

SYSU

 

Source

2016 Multi-University Training Contest 7

 

#include <iostream>

#include <cstdio>

#include <cstring>

#include <string>

#include <algorithm>

#include <cmath>

#include <map>

#include <cmath>

#include <set>

#include <stack>

#include <queue>

#include <vector>

#include <bitset>

#include <functional>

using namespace std;

#define LL long long

const int INF = 0x3f3f3f3f;

int n,x;

char s1[10],s2[5],s3[5];

int cnt [1000005],fl[1000006];

struct node

{

    int t,val;

    friend bool operator <(const node &a,const node &b)

    {

        return a.t<b.t;

    }

} pre;

int main()

{

    int cas=0;

    while(~scanf("%d",&n)&&n)

    {

        printf("Case #%d:\n",++cas);

        priority_queue<node>q1,q2,q3;

        for(int i=1; i<=n; i++)

        {

            scanf("%s",s1);

            if(!strcmp(s1,"push"))

            {

                scanf("%s%d",s2,&x);

                pre.t=i,pre.val=x;

                if(!strcmp(s2,"A")) q1.push(pre);

                else q2.push(pre);

            }

            else if(!strcmp(s1,"pop"))

            {

                scanf("%s",s2);

                if(!strcmp(s2,"A"))

                {

                    if(!q1.empty())

                        printf("%d\n",q1.top().val),q1.pop();

                    else

                        printf("%d\n",q3.top().val),q3.pop();

                }

                else

                {

                    if(!q2.empty())

                    printf("%d\n",q2.top().val),q2.pop();

                     else

                        printf("%d\n",q3.top().val),q3.pop();

                }

            }

            else

            {

                scanf("%s%s",s2,s3);

                    while(!q2.empty())

                        q3.push(q2.top()),q2.pop();

                    while(!q1.empty())

                        q3.push(q1.top()),q1.pop();

            }

        }

    }

    return 0;

}