Не работает пример из Шилдта

#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;
 
class sample {
    char *s;
public:
    sample();
    sample(const sample &ob);
    ~sample() { if(s) delete [] s;
                cout << "Освобождение s-памяти" << endl; }
    void show() { cout << s << endl; }
    void set(char *str);
    sample operator=(sample &ob);
};
 
sample::sample()
{
    s = new char('\0');
}
 
sample::sample(const sample &ob)
{
    s = new char[strlen(ob.s) + 1];
    strcpy(s, ob.s);
}
 
void sample::set(char *str)
{
    s = new char[strlen(str) + 1];
    strcpy(s, str);
}
 
sample sample::operator=(sample &ob)
{
    if(strlen(ob.s) > strlen(s)){
        delete [] s;
        s = new char[strlen(ob.s) + 1];
    }
    strcpy(s, ob.s);
    return *this;
}
 
sample input()
{
    char instr[80];
    sample str;
 
    cout << "Введите строку: ";
    cin >> instr;
 
    str.set(instr);
    return str;
}
 
int main()
{
    sample ob;
 
    ob = input();
    ob.show();
 
    return 0;
}

sample sample::operator=(sample ob)
{
    if(strlen(ob.s) > strlen(s)){
        delete [] s;
        s = new char[strlen(ob.s) + 1];
    }
    strcpy(s, ob.s);
    return *this;
}

sample sample::operator=(sample ob)

delete [] s;

cout << "Освобождение s-памяти" << endl;

#include <iostream>
#include <cstdlib>
#pragma warning(disable : 4996)
using namespace std;
class sample {
    char *s;
public:
    sample(); // normal constructor
    sample(const sample &ob); // copy constructor
    ~sample() { if (s) delete[] s; cout << "Freeing s\n"; }
    void show() { cout << s << "\n"; }
    void set(char *str);
    sample operator=(sample &ob); // overload assignment
};
// Normal constructor.
sample::sample()
{
    s = new char('\0'); // s points to a null string.
}
// Copy constructor.
sample::sample(const sample &ob)
{
    s = new char[strlen(ob.s) + 1];
    strcpy(s, ob.s);
}
// Load a string.
void sample::set(char *str)
{
    s = new char[strlen(str) + 1];
    strcpy(s, str);
}
// Overload assignment operator.
sample sample::operator=(sample &ob)
{
    /* If the target memory is not large enough
    then allocate new memory. */
    if (strlen(ob.s) > strlen(s)) {
        delete[] s;
        s = new char[strlen(ob.s) + 1];
    }
    strcpy(s, ob.s);
    return *this;
}
// Return an object of type sample.
sample input()
{
    char instr[80];
    sample str;
    cout << "Enter a string: ";
    cin >> instr;
    str.set(instr);
    return str;
}
int main()
{
    sample ob;
    // assign returned object to ob
    ob = input(); // This is now OK
    ob.show();
    return 0;
}