add code in doc

Author: daileyet

doc/20-备忘录.md

@@ -37,5 +37,132 @@
 
 [code](../code/19_memento)
 
-
+```c++
+// memento_types.h
+#ifndef __MEMENTO_TYPES_H__
+#define __MEMENTO_TYPES_H__
+
+#include <iostream>
+#include <string>
+#include <stack>
+using namespace std;
+
+class Step
+{
+public:
+    Step(std::string state) : state_(state) {}
+    ~Step() {}
+    inline std::string getState()
+    {
+        return state_;
+    }
+
+private:
+    std::string state_;
+};
+
+class Player
+{
+public:
+    Player();
+    ~Player();
+    Step *doAction(std::string state);
+    void applyAction(Step *step);
+
+private:
+    std::string state_;
+};
+
+class StepsManager
+{
+public:
+    StepsManager();
+    ~StepsManager();
+    void push(Step *step);
+    Step *pop();
+
+private:
+    std::stack<Step *> mementos;
+};
+
+#endif // __MEMENTO_TYPES_H__
+```
+
+```c++
+// memento_types.cpp
+#include "memento_types.h"
+
+Player::Player()
+{
+}
+
+Player::~Player()
+{
+}
+
+Step *Player::doAction(std::string state)
+{
+    this->state_ = state;
+    Step *step = new Step(this->state_);
+    cout << "Do step:" << this->state_ << endl;
+    return step;
+}
+
+void Player::applyAction(Step *step)
+{
+    if (step)
+    {
+        this->state_ = step->getState();
+        cout << "Back step:" << this->state_ << endl;
+    }
+}
+
+StepsManager::StepsManager()
+{
+}
+
+StepsManager::~StepsManager()
+{
+}
+
+void StepsManager::push(Step *step)
+{
+    if (step)
+    {
+        mementos.push(step);
+    }
+}
+
+Step *StepsManager::pop()
+{
+    Step *step = NULL;
+    if (mementos.empty())
+        return step;
+    step = mementos.top();
+    mementos.pop();
+    return step;
+}
+
+```
+
+```c++
+#include "memento_types.h"
+
+int main()
+{
+    Player player1;
+    StepsManager stepManager;
+    cout << "-----------" << endl;
+    stepManager.push(player1.doAction("车2平5"));
+    stepManager.push(player1.doAction("兵3进1"));
+    stepManager.push(player1.doAction("兵4平1"));
+
+    player1.applyAction(stepManager.pop());
+    player1.applyAction(stepManager.pop());
+    player1.applyAction(stepManager.pop());
+    cout << "-----------" << endl;
+    return 0;
+}
+
+```
 ![result](../code/19_memento/result.png)

doc/21-观察者.md

@@ -38,4 +38,133 @@
 
 [code](../code/20_observer)
 
+```c++
+// observer_types.h
+#ifndef __OBSERVER_TYPES_H__
+#define __OBSERVER_TYPES_H__
+
+#include <iostream>
+#include <string>
+#include <vector>
+using namespace std;
+
+class Buyer
+{
+public:
+    virtual ~Buyer() {}
+    virtual void action() = 0;
+};
+
+class Product
+{
+public:
+    Product() : amount(0) {}
+    virtual ~Product() {}
+    virtual void addBuyer(Buyer *buyer) = 0;
+    virtual void removeBuyer(Buyer *buyer) = 0;
+    virtual void notifyBuyers() = 0;
+    void setAmount(int amount)
+    {
+        this->amount = amount;
+        if (this->amount > 0)
+        {
+            std::cout << "Goods arrived!" << std::endl;
+            notifyBuyers();
+        }
+    }
+
+protected:
+    int amount;
+};
+
+class IPhoneX : public Product
+{
+public:
+    ~IPhoneX();
+    void addBuyer(Buyer *buyer);
+    void removeBuyer(Buyer *buyer);
+    void notifyBuyers();
+
+private:
+    vector<Buyer *> buyers;
+};
+
+class BuyerA : public Buyer
+{
+public:
+    void action();
+};
+
+class BuyerB : public Buyer
+{
+public:
+    void action();
+};
+
+#endif // __OBSERVER_TYPES_H__
+```
+```c++
+// observer_types.cpp
+#include "observer_types.h"
+
+void IPhoneX::addBuyer(Buyer *buyer)
+{
+    buyers.push_back(buyer);
+}
+
+void IPhoneX::removeBuyer(Buyer *buyer)
+{
+    for (vector<Buyer *>::iterator itr = buyers.begin();
+         itr != buyers.end(); itr++)
+    {
+        if (*itr == buyer)
+        {
+            buyers.erase(itr);
+            return;
+        }
+    }
+}
+
+void IPhoneX::notifyBuyers()
+{
+    for (vector<Buyer *>::iterator itr = buyers.begin();
+         itr != buyers.end();
+         itr++)
+    {
+        (*itr)->action();
+    }
+}
+
+void BuyerA::action()
+{
+    std::cout << "A: OK I will buy it." << std::endl;
+}
+
+void BuyerB::action()
+{
+    std::cout << "B: Take another look." << std::endl;
+}
+
+IPhoneX::~IPhoneX()
+{
+    buyers.clear();
+}
+
+```
+```c++
+// client.cpp
+#include "observer_types.h"
+
+int main(){
+    Product* ihponex = new IPhoneX();
+    Buyer* buyerA = new BuyerA();
+    Buyer* buyerB = new BuyerB();
+
+    ihponex->addBuyer(buyerA);
+    ihponex->addBuyer(buyerB);
+
+    ihponex->setAmount(100);
+    return 1;
+}
+```
 ![result](../code/20_observer/result.png)