Reversing string using stack

#include <bits/stdc++.h>
using namespace std;

// A structure to represent a stack
class Stack {
public:
	int top;
	unsigned capacity;
	char* array;
};


Stack* createStack(unsigned capacity)
{
	Stack* stack = new Stack();
	stack->capacity = capacity;
	stack->top = -1;
	stack->array
		= new char[(stack->capacity * sizeof(char))];
	return stack;
}

// Stack is full when top is equal to the last index
int isFull(Stack* stack)
{
	return stack->top == stack->capacity - 1;
}

// Stack is empty when top is equal to -1
int isEmpty(Stack* stack) { return stack->top == -1; }

// Function to add an item to stack.
// It increases top by 1
void push(Stack* stack, char item)
{
	if (isFull(stack))
		return;
	stack->array[++stack->top] = item;
}

char pop(Stack* stack)
{
	if (isEmpty(stack))
		return -1;
	return stack->array[stack->top--];
}

// A stack based function to reverse a string
void reverse(char str[])
{
	// Create a stack of capacity
	// equal to length of string
	int n = strlen(str);
	Stack* stack = createStack(n);

	// Push all characters of string to stack
	int i;
	for (i = 0; i < n; i++)
		push(stack, str[i]);

	for (i = 0; i < n; i++)
		str[i] = pop(stack);
}

// Driver code
int main()
{
	char str[] = "GeeksQuiz";

	reverse(str);
	cout << "Reversed string is " << str;

	return 0;
}