find the validity of first brackets

#include <stdio.h>
#include <stdlib.h>

// Structure to represent a stack
struct Stack {
    char* array;
    int top;
};

// Function to initialize an empty stack
void initializeStack(struct Stack* stack, int size) {
    stack->array = (char*)malloc(size * sizeof(char));
    stack->top = -1;
}

// Function to check if the stack is empty
int isEmpty(struct Stack* stack) {
    return (stack->top == -1);
}

// Function to push a character onto the stack
void push(struct Stack* stack, char ch) {
    stack->array[++stack->top] = ch;
}

// Function to pop a character from the stack
char pop(struct Stack* stack) {
    if (!isEmpty(stack)) {
        return stack->array[stack->top--];
    }
    return '\0'; // Return null character for an empty stack
}

// Function to check the validity of brackets
int isValidBrackets(char* expression) {
    struct Stack stack;
    initializeStack(&stack, 100); // Assuming a maximum size of 100 for the stack

    for (int i = 0; expression[i] != '\0'; i++) {
        char currentChar = expression[i];

        if (currentChar == '(' || currentChar == '[' || currentChar == '{') {
            push(&stack, currentChar);
        } else if (currentChar == ')' || currentChar == ']' || currentChar == '}') {
            if (isEmpty(&stack)) {
                return 0; // Unmatched closing bracket
            }

            char poppedChar = pop(&stack);

            // Check if the popped bracket matches the current closing bracket
            if ((currentChar == ')' && poppedChar != '(') ||
                (currentChar == ']' && poppedChar != '[') ||
                (currentChar == '}' && poppedChar != '{')) {
                return 0; // Mismatched opening and closing brackets
            }
        }
    }

    // Check if there are any unmatched opening brackets left in the stack
    return isEmpty(&stack);
}

// Main function to test bracket validity
int main() {
    char expression[100];

    printf("Enter a sequence of brackets: ");
    scanf("%s", expression);

    if (isValidBrackets(expression)) {
        printf("The brackets are valid.\n");
    } else {
        printf("The brackets are not valid.\n");
    }

    return 0;
}