C(InfixToPostfix)

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

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

void push(char c) {
    stack[++top] = c;
}

char pop() {
    return stack[top--];
}

int precedence(char c) {
    if (c == '+' || c == '-') return 1;
    if (c == '*' || c == '/') return 2;
    if (c == '^') return 3;
    return 0;
}

void infixToPostfix(char infix[]) {
    char postfix[100];
    int j = 0;

    for (int i = 0; i < strlen(infix); i++) {
        char c = infix[i];

        // operand
        if (isalnum(c)) {
            postfix[j++] = c;
        }
        // left bracket
        else if (c == '(') {
            push(c);
        }
        // right bracket
        else if (c == ')') {
            while (top != -1 && stack[top] != '(') {
                postfix[j++] = pop();
            }
            pop(); // remove '('
        }
        // operator
        else {
            while (top != -1 && precedence(c) <= precedence(stack[top])) {
                postfix[j++] = pop();
            }
            push(c);
        }
    }

    // remaining operators
    while (top != -1) {
        postfix[j++] = pop();
    }

    postfix[j] = '\0';
    printf("Postfix: %s", postfix);
}

int main() {
    char infix[] = "A+B*(C-D)";
    infixToPostfix(infix);
    return 0;
}