infixtopost.c

/*Experiment 3
C C Nipun Das
VML20CS066*/

#include <stdio.h>
#include <ctype.h>

char stack[100];
int top = -1;

void push(char x)
{
    stack[++top] = x;
}
char pop()
{
    if (top == -1)
        return -1;
    else
        return stack[top--];
}
int priority(char x)
{
    if (x == '(')
        return 0;
    if (x == '+' || x == '-')
        return 1;
    if (x == '*' || x == '/')
        return 2;
    if (x == '^')
        return 3;
    else
        return 0;
}
int main()
{
    char exp[100];
    char *e, x;
    printf("Enter the expression : ");
    scanf("%s", exp);
    printf("\n");
    e = exp;
    while (*e != '\0')
    {
        if (isalnum(*e))
            printf("%c ", *e);
        else if (*e == '(')
            push(*e);
        else if (*e == ')')
        {
            while ((x = pop()) != '(')
                printf("%c ", x);
        }
        else
        {
            while (priority(stack[top]) >= priority(*e))
            {
                printf("%c ", pop());
            }
            push(*e);
        }
        e++;
    }
    while (top != -1)
    {
        printf("%c ", pop());
    }
    return 0;
}

/*OUTPUT:

Enter the expression : a+b*(c^d-e)^(f+g*h)-i

a b c d ^ e - f g h * + ^ * + i -

*/