o8dDn3 - Online C Compiler & Debugging Tool

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

char stack[100][10];
int top = -1;
int index = 0;
char input[100];

void push(const char *s) {
    strcpy(stack[++top], s);
}

void pop() {
    top--;
}

void printStack() {
    for(int i = 0; i <= top; i++) printf("%s", stack[i]);
    printf("\n");
}

int reduce() {
    // Rule 1: E -> E + E
    if(top >= 2 &&
       strcmp(stack[top-2], "E") == 0 &&
       strcmp(stack[top-1], "+") == 0 &&
       strcmp(stack[top], "E") == 0) {
        pop(); pop(); pop();
        push("E");
        return 1;
    }

    // Rule 2: E -> E * E
    if(top >= 2 &&
       strcmp(stack[top-2], "E") == 0 &&
       strcmp(stack[top-1], "*") == 0 &&
       strcmp(stack[top], "E") == 0) {
        pop(); pop(); pop();
        push("E");
        return 1;
    }

    // Rule 3: E -> ( E )
    if(top >= 2 &&
       strcmp(stack[top-2], "(") == 0 &&
       strcmp(stack[top-1], "E") == 0 &&
       strcmp(stack[top], ")") == 0) {
        pop(); pop(); pop();
        push("E");
        return 1;
    }

    // Rule 4: E -> id
    if(top!=-1 && stack[top][0]>= 'a' && stack[top][0] <= 'z') {
        pop();
        push("E");
        return 1;
    }

    return 0; // No reduction applied
}

int main() {
    fgets(input, sizeof(input), stdin); // allow input with spaces

    while(input[index]) {
        if(isspace(input[index])) {
            index++; // skip whitespace
            continue;
        }

        char temp[2] = {input[index], '\0'};
        push(temp);
        index++;

        printf("Shift: ");
        printStack();

        while(reduce()) {
            printf("Reduce: ");
            printStack();
        }
    }

    if(top == 0 && strcmp(stack[0], "E") == 0)
        printf("string Accepted\n");
    else
        printf("string Rejected\n");

    return 0;
}