C program to convert a postfix notation to Infix

Written by siddhartha. Posted in Misc

Source Code

/*************************************************************************************/
/*  Write a C program to convert a postfix notation to Infix*/
/*  Download more programs at http://sourcecode4u.com/ */
/*************************************************************************************/
#include <stdio.h>
#include <stdlib.h>
int top = 10;
struct tree
{
  char ch;
  struct tree *next;
  struct tree *prev;
}  *stack[11];
typedef struct tree tree;

void push(tree *str)
{
  if (top <= 0)
    printf("Stack is Full ");
  else
  {
    stack[top] = str;
    top--;
  } 
}

tree *pop()
{
  tree *exp;
  if (top >= 10)
    printf("Stack is Empty ");
  else
    exp = stack[++top];
  return exp;
}


void convert(char exp[])
{
  tree *op1,  *op2;
  tree *temp;
  int i;
  for (i = 0; exp[i] != '\0'; i++)
  if (exp[i] >= 'a' && exp[i] <= 'z' || exp[i] >= 'A' && exp[i] <= 'Z')
  {
    temp = (tree*)malloc(sizeof(tree));
    temp->ch = exp[i];
    temp->next = NULL;
    temp->prev = NULL;
    push(temp);
  }
  else if (exp[i] == '+' || exp[i] == '-' || exp[i] == '*' || exp[i] == '/' ||
    exp[i] == '^')
  {
    op1 = pop();
    op2 = pop();
    temp = (tree*)malloc(sizeof(tree));
    temp->ch = exp[i];
    temp->next = op1;
    temp->prev = op2;
    push(temp);
  }
}

void display(tree *temp)
{
  if (temp != NULL)
  {
    display(temp->prev);
    printf("%c", temp->ch);
    display(temp->next);
  }
}

main()
{
  char exp[50];
  printf("Enter the postfix expression :");
  scanf("%s", exp);
  convert(exp);
  printf("\nThe Equivalant Infix expression is:");
  display(pop());
  printf("\n\n");
}

Out Put

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