[UVA] 11995 - I Can Guess the Data Structure! [STL应用]

11995 - I Can Guess the Data Structure!

Time limit: 1.000 seconds

Problem I

I 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 x without 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 1MB.

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

6

1 1

1 2

1 3

2 1

2 2

2 3

6

1 1

1 2

1 3

2 3

2 2

2 1

2

1 1

2 2

4

1 2

1 1

2 1

2 2

7

1 2

1 5

1 1

1 3

2 5

1 4

2 4

Output for the Sample Input

queue

not sure

impossible

stack

priority 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!

 

题解：STL中 queue、stack、priority_queue的使用。

代码：

 

 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     else

23     if(qui==0 && pri==1 && sti==0) printf("priority queue\n");

24     else

25     if(qui==0 && pri==0 && sti==1) printf("stack\n");

26     else

27     if(qui==0 && pri==0 && sti==0) printf("impossible\n");

28     else

29     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 }