Legendary Data Structure

Legendary Data Structure Time Limit: 1000 ms memory limit: 65536 k any questions? Click Here ^_^ I have been studying at the university for one semester. Most people have a basic understanding of the major they have learned. Many of you have learned that a course will be held in your sophomore year called "Data Structure". Today we will give you a brief introduction to the simplest Data Structure: Stack. There are three basic stack operations: Push, pop, and top.
For example, give you a series: 1 2 3 4  
Push: Add a number to the stack, for example, Push 5. The number of columns is 1, 2, 4, and 5.
Pop: Delete the last number from the stack, for example, Pop. The number of columns is 1 2 3. (The number of columns is changed but not output. If the stack is empty, that is, the pop operation is not allowed, an error is output, but the next operation will continue ). 
Top: Find the number at the end of the stack, such as top, and you need to output 4. (If there is no number in the stack, that is, the top operation is not allowed, then empty is output ).
Then, you can see that, in fact, the stack is a data structure that comes out first (the more advanced the elements come out later). It is very simple, next we will test your learning performance. Input

The input contains multiple groups of test data.
The first behavior of each group of data is an integer T (1 <=t <= 1000), followed by the T action on the stack operation.

Output

If the operation is top, the final number is output. If there is no number in the stack, the "empty" is output (excluding quotation marks ).
If the operation is pop and the stack is empty, an error is output (excluding quotation marks ).
Add a line feed to the last test data of each group.

Sample Input

 
8 Push 1 Push 2 Push 3 push 4toppoptoppop3push 1 PopTop
 

Sample output

 
43 empty
 

Prompt source Qinchuan sample program

# Include <stdio. h> # include <stdlib. h> # include <string. h> int main () {char st [20]; int t, n, j = 0; int num [1, 1002]; while (~ Scanf ("% d", & T) {getchar (); j = 0; memset (Num, 0, sizeof (Num); While (t --) {scanf ("% s", St); If (strcmp (St, "push") = 0) {scanf ("% d", & N ); num [J ++] = N;} else if (strcmp (St, "TOP") = 0) {If (J! = 0) printf ("% d \ n", num [J-1]); else printf ("Empty \ n");} else if (strcmp (St, "pop ") = 0) {If (j = 0) printf ("error \ n"); else j -- ;}} printf ("\ n") ;}return 0 ;}