#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");
}
