String, invertir una cadena

int main() {

stack s(100);
std::string str;
getline (std::cin, str);
for (int i = 0; i < str.length(); i++) s.push(str[i]);
s.print();
return 0;
}

stack::node::node(char x) {
_data = x;
_next = nullptr;
}

stack::stack(int m){

n = m;
s = 0;

init = nullptr;
}

stack::~stack(){

while(init != nullptr) {
node *p = init;
init = init->next();
delete p;
}

}

void stack::push(char x){

assert(!full());
node *p = new node(x);
p -> next(init);
init = p;

s++;
}

void stack::print(){

node *p = init;
while(p != nullptr){
std::cout << p -> data();
p = p -> next();
}
}

#include <iostream>
#include <assert.h>
#include <string>

class stack {

class node {

char _data;
node *_next;

public:

node(char);

char data() const { return _data; } //cual es el dato
node *next() const { return _next; } // cual es el siguiente apuntador
void next(node *p) { _next = p; } // cambia el siguiente ap
};

int n; // Capacity of stack
int s; // Size of stack

node *init; // Inicio de nodo

public:

stack(int);
~stack();

void push(char);

int capacity() const { return n; }
int size() const { return s; }

bool full() const { return s==n; }
bool empty() const { return s==0; }

void print();
};

#endif /* string_hpp */