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

#define MAX_SIZE 100

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

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

char pop() {
    if (top < 0) {
        printf("Stack Underflow\n");
        return -1;
    }
    return stack[top--];
}

int precedence(char symbol) {
    switch (symbol) {
        case '^': return 3;
        case '*':
        case '/': return 2;
        case '+':
        case '-': return 1;
        default: return 0;
    }
}

void reverse(char *str) {
    int len = strlen(str);
    int i, j;
    char temp;
    for (i = 0, j = len - 1; i < j; i++, j--) {
        temp = str[i];
        str[i] = str[j];
        str[j] = temp;
    }
}

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

void infixToPrefix(char infix[], char prefix[]) {
    char symbol, temp[2];
    int i, j = 0;
    
    reverse(infix);
    
    for (i = 0; infix[i] != '\0'; i++) {
        symbol = infix[i];
        if (isalnum(symbol)) {
            prefix[j++] = symbol;
        } else if (symbol == ')') {
            push(symbol);
        } else if (symbol == '(') {
            while ((temp[0] = pop()) != ')') {
                prefix[j++] = temp[0];
            }
        } else {
            while (top > -1 && precedence(stack[top]) > precedence(symbol)) {
                prefix[j++] = pop();
            }
            push(symbol);
        }
    }
    
    while (top > -1) {
        prefix[j++] = pop();
    }
    prefix[j] = '\0';
    
    reverse(prefix);
}

int main() {
    char infix[MAX_SIZE], prefix[MAX_SIZE];
    printf("Enter infix expression: ");
    fgets(infix, MAX_SIZE, stdin);
    infix[strcspn(infix, "\n")] = 0;  // Remove newline if present
    infixToPrefix(infix, prefix);
    printf("Prefix expression: %s\n", prefix);
    return 0;
}