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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4. #include <math.h>
  5. #define SIZE  100
  6. int count=0;
  7. typedef struct node{
  8.  int value;
  9.  struct stack *next;
  10.  struct stack *prev;
  11. }stack;
  12.  
  13. stack *bottom=NULL;
  14. stack *top=NULL;
  15.  
  16. stack *createnode(int a)
  17. {
  18.  stack *newstack;
  19.  newstack=(stack*)calloc(1,sizeof(stack));
  20.  newstack->value=a;
  21.  newstack->prev=NULL;
  22.  newstack->next=NULL;
  23.  return newstack;
  24. }
  25.  
  26. int isempty()
  27.    {
  28.        if(count==0)
  29.        {return 1;}
  30.        else
  31.        {return 0;}
  32.     }
  33.  
  34. int isfull()
  35.     {
  36.      if(count==SIZE)
  37.      {return 1;}
  38.      else
  39.      {return 0;}
  40.     }
  41.  
  42. void push(int a)
  43. {   if(isfull()==1)
  44.    {
  45.     printf("overflow condition: stack full");
  46.    }
  47.  else
  48.    {count+=1;
  49.  stack *newstack = createnode(a);
  50.  if(bottom==NULL)
  51.  {
  52.  bottom=newstack;
  53.  top=bottom;
  54.  }
  55.  else
  56.  {
  57.   top->next=newstack;
  58.   newstack->prev=top;
  59.   top=newstack;
  60.  }
  61.    }
  62. }
  63. char peek()
  64. {
  65.     return top->value;
  66. }
  67. char pop()
  68.     {   if(isempty()==1)
  69.         {
  70.          printf("underflow condition:empty stack");
  71.         }
  72.         else
  73.         {if(count==1)
  74.         {   int c;
  75.          c=top->value;
  76.          top=NULL;
  77.          bottom=NULL;
  78.          count=count-1;
  79.          return c;
  80.  
  81.         }
  82.         else
  83.      {int c;
  84.      c=top->value;
  85.   top=top->prev;
  86.   top->next=NULL;
  87.   count=count-1;
  88.   return c;
  89.  
  90.      }
  91.        }
  92.     }
  93.     char plus=43;
  94.     char multi=42;
  95.     char divi=47;
  96.     char power=94;
  97.     char left=40;
  98.     char right=41;
  99.     char subtract=45;
  100. void *postfix_evaluation(char *string,int length)
  101. {  int i; stack operators;
  102.  for(i=0;i<length;i++)
  103.  {
  104.   char c;
  105.   c=string[i];
  106.   if(c==plus || c==subtract || c==multi || c==divi || c==power)
  107.   {
  108.         int a =pop();
  109.         int b=pop();
  110.         if(c==plus)
  111.         {
  112.                 int result=b+a;
  113.                 push(result);
  114.              //   printf("%d",result);
  115.         }
  116.         if(c==subtract)
  117.         {
  118.                 int result=b-a;
  119.                 push(result);
  120.         }
  121.         if(c==multi)
  122.         {
  123.                 int result=b*a;
  124.                 push(result);
  125.         }
  126.         if(c==divi)
  127.         {
  128.                 int result=b/a;
  129.                 push(result);
  130.         }
  131.         if(c==power)
  132.         {
  133.                 int result=pow(b,a);
  134.                 push(result);
  135.         }
  136.         }
  137.         else
  138.         {     int k=c-'0';
  139.               push(k);
  140.           //    printf("%d",k);
  141.         }
  142. /*  if(i==length-1)
  143.   {    
  144.         int d=pop();
  145.         printf("%d",d);
  146.   }
  147. */  
  148.   }
  149.   int d=pop();
  150.   printf("%d",d);
  151. }
  152.  
  153. // driver code , the main function
  154.  
  155. int main(void)
  156. {   char inversion[200];
  157.  printf("give the postfix expression\n");
  158.  scanf("%s",&inversion);
  159.  int longer=strlen(inversion);
  160.  postfix_evaluation(inversion,longer);
  161.  
  162.  return 0;
  163. }
  164.  
Success #stdin #stdout 0s 9424KB
comments (?)
stdin 
23+3^
stdout 
give the postfix expression
125
https://ideone.com/hcTiOj
language:
C (gcc 8.3)
created:
5 years ago
visibility:
public

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