[Ultraviolet A] 11995-I can guess the data structure! [STL application]

11995-I can guess the data structure! Time Limit: 1.000 secondsProblem II can guess the data structure!

There is a bag-like data structure, supporting two operations:

1 x

Throw an element x into the bag.

2

Take out an element from the bag.

Given a sequence of operations with return values, you're going to guess the data structure. it is a stack (last-in, first-out), a queue (first-in, first-out), a priority-queue (always take out larger elements first) or something else that you can hardly imagine!

Input

There are several test cases. each test case begins with a line containing a single integer N (1 <= n <= 1000 ). each of the next n lines is either a type-1 command, or an integer 2 followed by an integer x. that means after executing a type-2 command, we get an element xWithout Error. The value of X is always a positive integer not larger than 100. The input is terminated by end-of-file (EOF). The size of input file does not exceed 1 MB.

Output

For each test case, output one of the following:

stack

It's definitely a stack.

queue

It's definitely a queue.

priority queue

It's definitely a priority queue.

impossible

It can't be a stack, a queue or a priority queue.

not sure

It can be more than one of the three data structures mentioned above.

Sample Input

61 11 21 32 12 22 361 11 21 32 32 22 121 12 241 21 12 12 271 21 51 11 32 51 42 4

Output for the sample input

queuenot sureimpossiblestackpriority queue

Rujia Liu's present 3: a data structure contest celebrating the 100th Anniversary of Tsinghua University
Special thanks: yiming Li
Note: Please make sure to test your program with the gift I/O files before submitting!

 

Question: Use of queue, stack, and priority_queue in STL.

Code:

 

 1 #include<cstdio> 2 #include<cstring> 3 #include<stdbool.h> 4 #include<cmath> 5 #include<queue> 6 #include<stack> 7 #include<algorithm> 8  9 10 #define rep(i,a,b)      for(i=(a);i<=(b);i++)11 #define red(i,a,b)      for(i=(a);i>=(b);i--)12 #define clr(x,y)        memset(x,y,sizeof(x))13 #define sqr(x)          ((x)*(x))14 15 using namespace std;16 17 int i,j,x,y,pri,qui,sti;18     19 void check()20 {21     if(qui==1 && pri==0 && sti==0) printf("queue\n");22     else23     if(qui==0 && pri==1 && sti==0) printf("priority queue\n");24     else25     if(qui==0 && pri==0 && sti==1) printf("stack\n");26     else27     if(qui==0 && pri==0 && sti==0) printf("impossible\n");28     else29     printf("not sure\n");   30 }31 32 int main()33 {34     int T;35     36    37     38     while(scanf("%d",&T)!=EOF) {39          pri=qui=sti=1;40         41          queue <int> Q;42          stack <int> S;43          priority_queue <int> prQ;44         45         while(T--) {46             scanf("%d%d",&x,&y);47             if(x==1) {48                 Q.push(y);49                 S.push(y);50                 prQ.push(y);51             } 52               else {53                54                   if(qui==1) {55                     if(Q.empty() || Q.front()!=y) qui=0;56                     if(!Q.empty()) Q.pop();57                   }58                    59                   if(sti==1) {60                     if(S.empty() || S.top()!=y) sti=0;61                     if(!S.empty()) S.pop();62                   }   63       64                   if(pri==1) {65                     if(prQ.empty() || prQ.top()!=y) pri=0;66                     if(!prQ.empty()) prQ.pop();67                   }          68              }    69         }70            71             check();72     }73     74     return 0;75 }

 

[Ultraviolet A] 11995-I can guess the data structure! [STL application]