1 #include <iostream>
  2 
  3 using namespace std;
  4 
  5 template <typename K, typename V>
  6 class BST
  7 {
  8     private:
  9         struct node    // 类内定义类、结构体
 10         {
 11             K key;
 12             V value;
 13             node *left = nullptr;
 14             node *right = nullptr; 
 15         };
 16         node * root = nullptr;
 17         node * putB(node *rootp, K key, V value);   // 注意不能把这个函数放在公有区，因为node是一个私有变量，如果外部调用putB会出问题，且只有成员函数会调用这个函数，没必要声明为公有的就不要声明为公有
 18     public:
 19         BST(/* args */);
 20         void putA(K key, V value);
 21         void putB(K key, V value);
 22         /* void putB(node *&rootp, K key, V value); */  //类内定义结构体不用加作用域限定：  BST<K, V>::node
 23         
 24         V get(K key);
 25         V getR(node *rootp, K key);     //对于结构相似且头尾相接的数据结构（如这里的二叉树：每个节点都可以是根节点，每个根节点下都有左右节点），要善于利用递归
 26         bool max(K &key, V &value);
 27         bool min(K &key, V &value);
 28         int rank(K key);
 29         bool remove(K key);
 30         int howMany();
 31         void show();
 32         void showR(node *p);
 33         void free(node *p);
 34         ~BST(); 
 35 };
 36 
 37 template <typename K, typename V>
 38 BST<K, V>::BST(/* args */)
 39 {
 40     //did nothing
 41 }
 42 
 43 template <typename K, typename V>
 44 V BST<K, V>::get(K key)
 45 {
 46     V val = NULL;
 47     val = getR(root, key);
 48     if(val != NULL)    //warning：val == 0  is equal to val == NULL
 49     {
 50         cout << "key: " << key << "\t val: " << val << endl;
 51         return val;
 52     }
 53 }
 54 
 55 template <typename K, typename V>
 56 V BST<K, V>::getR(node *rootp, K key)
 57 {
 58     if(rootp == nullptr)
 59     {
 60         cout << "can't find key[" << key << "]." << endl;
 61         return NULL;
 62     }
 63         
 64     if(rootp->key == key)
 65         return rootp->value;
 66     else if(rootp->key < key)
 67     {
 68         return getR(rootp->right, key);
 69     }
 70     else 
 71         return getR(rootp->left, key);
 72 }
 73 
 74 /* 循环查找 */
 75 template <typename K, typename V>
 76 void BST<K, V>::putA(K key, V value)
 77 {
 78     node **temp = &root;    //使用指针的指针，因为下面要给指针分配内存
 79     while((*temp) != nullptr)
 80     {
 81         if((*temp)->key == key)
 82         {
 83             (*temp)->key = key;
 84             (*temp)->value = value;
 85             return;
 86         }
 87         if((*temp)->key > key)
 88             temp = &((*temp)->left);
 89         else 
 90             temp = &((*temp)->right);
 91     }
 92     *temp = (node *)new node;
 93     (*temp)->key = key;
 94     (*temp)->value = value;
 95 }
 96 
 97 template <typename K, typename V>
 98 void BST<K, V>::putB(K key, V value)
 99 {
100     /* putB(root, key, value); */
101     root = putB(root, key, value);
102 }
103 
104 /* 递归查找 */
105 /* 
106 template <typename K, typename V>
107 void BST<K, V>::putB(node *&rootp, K key, V value)   //指针的引用
108 {
109     if(rootp == nullptr)
110     {
111         rootp = new node;
112         rootp->key = key;
113         rootp->value = value;
114         return;
115     }
116     if(rootp->key == key)
117     {
118         rootp->value = value;
119         return;
120     }
121     else if(rootp->key > key)
122         return putB(rootp->left, key, value);
123     else
124         return putB(rootp->right, key, value);
125     
126 }
127  */
128 
129 /* 不加typename的话会提示错误： need 'typename' before 'BST<K, V>::node' because 'BST<K, V>' is a dependent scope，原因：c++primer P593 */
130 template <typename K, typename V>
131 typename BST<K, V>::node * BST<K, V>::putB(node *rootp, K key, V value)   
132 {
133     if(rootp == nullptr)
134     {
135         rootp = new node;
136         rootp->key = key;
137         rootp->value = value;
138         return rootp;
139     }
140     if(rootp->key == key)
141     {
142         rootp->value = value;
143     }
144     else if(rootp->key > key)
145         rootp->left =  putB(rootp->left, key, value);
146     else
147         rootp->right = putB(rootp->right, key, value);
148 
149     return rootp;
150 }
151 
152 template <typename K, typename V>
153 void BST<K, V>::show()
154 {
155     showR(root);
156 }
157 
158 template <typename K, typename V>
159 void BST<K, V>::showR(node *p)
160 {
161     if(p->left != nullptr)
162         showR(p->left);
163     cout << "key: " << p->key << "\tvalue: " << p->value << endl;
164     if(p->right != nullptr)
165         showR(p->right);
166 }
167 
168 template <typename K, typename V>
169 void BST<K, V>::free(node *p)
170 {
171     if(p == nullptr)
172         return;
173     free(p->left);
174     free(p->right);
175     delete p;
176 }
177 
178 template <typename K, typename V>
179 BST<K, V>::~BST()
180 {
181     free(root);
182 }
183 
184 int main()
185 {
186     BST<char, int> container;
187     cout << "before: " << endl;
188     for(int i=0; i<22; ++i)
189     {
190         char k = 65 + rand() % 20;
191         int v = rand() % 100;
192         cout << "k: " << k << "    v: " << v << endl;
193         container.putB(k, v);
194         //or container.putA(k, v);
195     }
196     
197     container.show();
198 
199     char token;
200     cout << "enter key you want to find(0 to exit):"; 
201     cin >> token;
202     while(token != '0')
203     {
204         container.get(token);
205         cout << "enter key you want to find(0 to exit):";
206         cin >> token;
207     }
208     
209     return 0;
210 }