面試的題目：
//
// main.cpp
// truetelCodingQuestions
//
// Created by BH_Lin on 2019/2/12.
// Copyright © 2019 Studio Bing-Huan. All rights reserved.
/*
Coding Question for Company: https://www.104.com.tw/jobbank/custjob/index.php?r=cust&j=483a446b565c3f2238423a1d1d1d1d5f2443a363189j56
http://truetel.com/
*/
#include <iostream>
using namespace std;
// ---------------------------------------------------------------------------->
/* Coding Question 1:
Description: Try to exchange two values without using any extra variable.
*/
void exchange(int *a, int *b)
{
cout << ">> exchange" << endl;
*a = *a + *b;
*b = *a - *b;
*a = *a - *b;
}
// ----------------------------------------------------------------------------<
// ---------------------------------------------------------------------------->
/* Coding Question 2:
Description: What the output will be.
*/
class Base {
public:
Base() {
cout<< "Base Constructor " << endl;
}
~Base() {
cout<< "Base Destructor " << endl;
}
};
class Derived: public Base {
public:
Derived() {
cout<< "Derived Constructor " << endl;
}
~Derived() {
cout<< "Derived Destructor " << endl;
}
};
class Base2 {
public:
Base2() {
cout<< "Base Constructor " << endl;
}
virtual ~Base2() {
cout<< "Base Destructor " << endl;
}
};
class Derived2: public Base2 {
public:
Derived2() {
cout<< "Derived Constructor " << endl;
}
~Derived2() {
cout<< "Derived Destructor " << endl;
}
};
// ----------------------------------------------------------------------------<
// ---------------------------------------------------------------------------->
/* Coding Question 4:
Description: Have a design pattern for singleton.
*/
class Lock {
public:
Lock() {}
~Lock() {}
void AcquireLock() {}
void ReleaseLock() {}
};
template<class T> class Singleton
{
// Write the implementation here.
private:
static T* m_pInstance;
Singleton(){}
public:
static T *instance() {
if(!m_pInstance) {
m_pInstance = new T;
}
return m_pInstance;
}
};
template <class T> T* Singleton<T>::m_pInstance=NULL;
class Foo {
private:
int i;
public:
Foo() {i=0;}
void test() {
cout<< "i is " << i << endl;
i++;
}
};
// ----------------------------------------------------------------------------<
int main(int argc, const char * argv[]) {
// ------------------------------------------------------------------------>
/* Coding Question 1:
Description: Try to exchange two values without using any extra variable.
*/
int a = 1;
int b = 2;
cout << "## Before exchanging" << endl;
cout << "a: " << a <<endl;
cout << "b: " << b <<endl;
exchange(&a,&b);
cout << "## After exchanging" << endl;
cout << "a: " << a <<endl;
cout << "b: " << b <<endl;
// ------------------------------------------------------------------------<
// ------------------------------------------------------------------------>
/* Coding Question 2-1:
Description: What the output will be.
*/
cout << "## Question 2-1 ##" << endl;
Base *p = new Derived();
delete p;
// Anwser is: The father's constructor/destructor will be called
// before child's constructor/destructor
// Base Constructor
// Derived Constructor
// Base Destructor
/* Coding Question 2-2:
Description: What the output will be.
If add Keyword "Virtual in front of the ~Base()
*/
cout << "## Question 2-2 ##" << endl;
Base2 *p2 = new Derived2();
delete p2;
// Anwser is:
// Base Constructor
// Derived Constructor
// Derived Destructor
// Base Destructor
// ------------------------------------------------------------------------<
// ------------------------------------------------------------------------>
/* Coding Question 4-1:
Description: Have a design pattern for singleton.
*/
Foo* singleton_foo = Singleton<Foo>::instance();
singleton_foo->test();
Foo* singleton_fool = Singleton<Foo>::instance();
singleton_fool->test();
// Next Design if for thread safe.
// ------------------------------------------------------------------------<
return 0;
}