MIT-Curricular/DS/C/Lab/Week6/PrefixToInfix.c

#include <stdio.h>
#include <string.h>

#define MAX_SIZE 100

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

void push(const char *item)
{
    if (top >= MAX_SIZE - 1)
    {
        printf("Stack Overflow\n");
        return;
    }
    strcpy(stack[++top], item);
}

char *pop()
{
    if (top < 0)
    {
        printf("Stack Underflow\n");
        return NULL;
    }
    return stack[top--];
}

int isOperator(char c)
{
    return (c == '+' || c == '-' || c == '*' || c == '/');
}

int isAlphanumeric(char c)
{
    return ((c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'));
}

void prefixToInfix(char *prefix)
{
    int len = strlen(prefix);
    char temp[MAX_SIZE];

    for (int i = len - 1; i >= 0; i--)
    {
        if (isAlphanumeric(prefix[i]))
        {
            temp[0] = prefix[i];
            temp[1] = '\0';
            push(temp);
        }
        else if (isOperator(prefix[i]))
        {
            char op1[MAX_SIZE], op2[MAX_SIZE], result[MAX_SIZE];
            strcpy(op1, pop());
            strcpy(op2, pop());
            sprintf(result, "(%s%c%s)", op1, prefix[i], op2);
            push(result);
        }
    }

    printf("Infix expression: %s\n", stack[top]);
}

int main()
{
    char prefix[MAX_SIZE];
    printf("Enter prefix expression: ");
    gets(prefix);

    prefixToInfix(prefix);

    return 0;
}