Solved

Problem in stack(data structure in C)

Posted on 1998-11-19
4
428 Views
Last Modified: 2010-04-15
How to write a program using stack (in C language)which functions almost like a calculator. the program will receive inputs like for example : 12 * (15 - 6) + 388  
The program will calculate +, -, *, /, (), operations.  
The priority operations are :

   1st. ( )
   2nd. *, /
   3rd. +, -

The program will print the operation for example like The question above :

15 - 6
12 * 9
108 + 388
= 496
0
Comment
Question by:tagheuer
  • 2
4 Comments
 
LVL 8

Expert Comment

by:Answers2000
Comment Utility
Easiest Answer is to write convert command strings to RPN (Reverse Polish Notation)

Basically this is a stack machine, you push values on the stack.  Operations then pull last 2 items and do the work

e.g.
15 - 6 becomes 15 6 -
15 is pushed on stack
6 is pushed on stack
- pulls last 2 items from stack, does the operation
- pushes the result back on stack

15 - 6 + 4 becomes 15 6 - 4 +
same idea
0
 
LVL 4

Accepted Solution

by:
emmons earned 10 total points
Comment Utility
Some code from imlandris...
#include "stdio.h"

#define Err(n)       printf(errm[n-1])
#define Guard(n)     if(sp<n-1){ Err(1); break; }

char errm[3][40] = { "Insufficient stack elements\n",
                     "Stack full\n",
                     "Invalid input\n"
                   };

char base = 'd',buf[160];
int cp=0;

main()

{       long stk[10],mem,sp;
        int i;
        char c,num[20];

        sp=-1;
        mem=0;

        do
        {       c=getnext();
                switch(c)
                {       case 'x':
                                base='x';
                                if(sp>=0)
                                {       printf("\n");
                                        show(stk[sp]);
                                }
                                break;
                        case 'd':
                                base='d';
                                if(sp>=0)
                                {       printf("\n");
                                        show(stk[sp]);
                                }
                                break;
                        case '+':
                                Guard(2);
                                stk[sp-1]+=stk[sp];
                                --sp;
                                printf("\n");
                                show(stk[sp]);
                                break;
                        case '-':
                                Guard(2);
                                stk[sp-1]-=stk[sp];
                                --sp;
                                printf("\n");
                                show(stk[sp]);
                                break;
                        case '*':
                                Guard(2);
                                stk[sp-1]*=stk[sp];
                                --sp;
                                printf("\n");
                                show(stk[sp]);
                                break;
                        case '/':
                                Guard(2);
                                stk[sp-1]/=stk[sp];
                                --sp;
                                printf("\n");
                                show(stk[sp]);
                                break;
                        case 't':
                                printf("\n");
                                if(sp>=0)show(stk[sp]);
                                break;
                        case 'a':
                                printf("\n");
                                for(i=sp; i>=0; --i)show(stk[i]);
                                break;
                        case 'p':
                                Guard(1);
                                --sp;
                                break;
                        case 's':
                                mem=stk[sp];
                                break;
                        case 'r':
                                stk[sp]=mem;
                                break;
                        case 'm':
                                printf("\n");
                                show(mem);
                                break;
                        case 'q':
                        case '\n':
                        case '\r':
                        case ' ':
                                break;
                        default:
                                if('0'<=c && c<='9')
                                {       if(sp<9)
                                        {       backup();
                                                getnum(num);
                                                ++sp;
                                                if(base=='d')sscanf(num,"%ld",stk+sp);
                                                else sscanf(num,"%lx",stk+sp);
                                        }
                                        else Err(2);
                                }
                                else Err(3);
                }
        } while(c!='q');
}


show(a)
long a;

{       if(base=='d')printf("%ld\n",a);
        else printf("%lx\n",a);
        return;
}

getnext()

{       if(buf[cp]=='\0')getline();
        return(buf[cp++]);
}


backup()

{       if(cp>0)--cp;
        return;
}


getnum(num)
char *num;

{       int dp;

        dp=0;
        while( ('0'<=buf[cp] && buf[cp]<='9') || (base=='x' && 'a'<=buf[cp] && buf[cp]<='f') )num[dp++]=buf[cp++];
        num[dp]='\0';
        return;
}


getline()

{       char *sp,*dp;

        scanf("%s",buf);
        dp=buf;
        for(sp=buf; *sp!='\0'; ++sp)
        {       if(*sp!=8)*dp++=*sp;
                else dp=dp>buf?dp-1:dp;
        }
        *dp='\0';
        cp=0;
        return;
}
0
 

Author Comment

by:tagheuer
Comment Utility
Theres a good one!!, any way thanks to you for helping me. I'll retype your codes and give you the feedback.
Actually I'm very new in C language especially in data sturcture chapter. May be you can help me (give an example on stack, recursion, queues and list).
Thank you again!!


0
 

Author Comment

by:tagheuer
Comment Utility
to: answer2000,
Can you explain more details on your suggestion above to convert command strings to RPN (Reverse Polish Notation). I'm really don't understand. It will be better if yu can give some example.

thanks!!
0

Featured Post

Do You Know the 4 Main Threat Actor Types?

Do you know the main threat actor types? Most attackers fall into one of four categories, each with their own favored tactics, techniques, and procedures.

Join & Write a Comment

Summary: This tutorial covers some basics of pointer, pointer arithmetic and function pointer. What is a pointer: A pointer is a variable which holds an address. This address might be address of another variable/address of devices/address of fu…
Windows programmers of the C/C++ variety, how many of you realise that since Window 9x Microsoft has been lying to you about what constitutes Unicode (http://en.wikipedia.org/wiki/Unicode)? They will have you believe that Unicode requires you to use…
The goal of this video is to provide viewers with basic examples to understand and use structures in the C programming language.
Video by: Grant
The goal of this video is to provide viewers with basic examples to understand and use while-loops in the C programming language.

744 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

20 Experts available now in Live!

Get 1:1 Help Now