light oj 1212 - Double Ended Queue (双向队列)

1212 - Double Ended Queue

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Time Limit: 0.5 second(s)

Memory Limit: 32 MB

A queue is a data structure based on the principle of 'First In First Out' (FIFO). There are two ends; one end can be used only to insert an item and the other end to remove an item. A Double Ended Queue is a queue where you can insert an item in both sides
as well as you can delete an item from either side. There are mainly four operations available to a double ended queue. They are:

1.      pushLeft(): inserts an item to the left end of the queue with the exception that the queue is not full.

2.      pushRight(): inserts an item to the right end of the queue with the exception that the queue is not full.

3.      popLeft(): removes an item from the left end of the queue with the exception that the queue is not empty.

4.      popRight(): removes an item from the right end of the queue with the exception that the queue is not empty.



Now you are given a queue and a list of commands, you have to report the behavior of the queue.

Input

Input starts with an integer T (≤ 20), denoting the number of test cases.

Each case starts with a line containing two integers n, m (1 ≤ n ≤ 10, 1 ≤ m ≤ 100), where n denotes the size of the queue and m denotes the number of commands. Each of the next m lines
contains a command which is one of:

pushLeft x        pushes x (-100 ≤ x ≤ 100) in the left end of the queue

pushRight x      pushes x (-100 ≤ x ≤ 100) in the right end of the queue

popLeft             pops an item from the left end of the queue

popRight           pops an item from the right end of the queue

Output

For each case, print the case number in a line. Then for each operation, show its corresponding output as shown in the sample. Be careful about spelling.

Sample Input	Output for Sample Input
1 3 8 pushLeft 1 pushLeft 2 pushRight -1 pushRight 1 popLeft popRight popLeft popRight	Case 1: Pushed in left: 1 Pushed in left: 2 Pushed in right: -1 The queue is full Popped from left: 2 Popped from right: -1 Popped from left: 1 The queue is empty

 双向队列，如上图，左右两端都可以既队列又出队列；

解：这题的数据不大，开一个数组，从中间开始模拟队列的进出

代码：

/*
l, r 是加是减 用具体几个数试试就清楚了
*/

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
int main()
{
int t,k=1,n,m,x,l,r;
int a[30]; //队列已经限制小于10
char str[20];
cin>>t;
while(t--)
{
cout<<"Case "<<k++<<":"<<endl;
int l=r=15;//从中间开始
cin>>n>>m;
for(int i=0;i<m;i++)
{
cin>>str;
if(str[1]=='u')//进队列的情况
{
cin>>x;
if(r-l>=n)
cout<<"The queue is full"<<endl;
else
{
if(str[4]=='L')
{
cout<<"Pushed in left: "<<x<<endl;
a[l]=x;l--;
}
else
{
cout<<"Pushed in right: "<<x<<endl;
r++;a[r]=x;
}
}
}
else//出队列的情况
{
if(l==r)
cout<<"The queue is empty"<<endl;
else
{
if(str[3]=='L')
{
cout<<"Popped from left: "<<a[l+1]<<endl;
l++;
}
else
{
cout<<"Popped from right: "<<a[r]<<endl;
r--;
}
}
}
}
}
return 0;
}