一個簡單的多叉樹實現：

1. 利用迭代器方便地構建樹，
2. 可以遞迴輸出，前序，後序。
3. 利用棧實現輸出。
4. 銷燬樹只能後序遍歷

類的定義：

#include <iostream> #include <string> #include <vector> #include <stack> #include <cassert> using namespace std; template<class T> class htree_node{ public: typedef htree_node<T> node_type; htree_node() :parent(0),format(" ") {} htree_node(const T& x) :name(x), parent(0), format(" ") {} ~htree_node() {} T name; //預設為兩個空格 std::string format; node_type *parent; std::vector<node_type*> children; }; template<class T, class Container = htree_node<T> > class htree{ protected: typedef Container tree_node; public: htree() :root(0) { Init(); } htree(tree_node *node) :root(node) { Init(); } ~htree(){ destroy(root); } //pre_order_iterator class iterator{ public: iterator() : _node(0) , skip_current_children_(false) { skip_children(); } iterator(tree_node *node) : _node(node) , skip_current_children_(false) { skip_children(); } ~iterator() {} T& operator*() const { return _node->name; } T* operator->() const { return &(_node->name); } tree_node* get() { return _node; } //開始位置 iterator begin() const { return iterator(_node); } //結束位置 const???? iterator end() const { return iterator( _find_end(_node) ); } tree_node *_node; protected: bool skip_current_children_; void skip_children() { skip_current_children_=true; } tree_node* _find_end(tree_node* current) const { int pos = current->children.size()-1; if( pos<0 ) return (current); //這裡返回iterator會被析構掉，臨時物件 //從最後一個孩子找起， else _find_end(current->children[pos]); } }; public: //注意傳position的引用 iterator insert(iterator& position, const T& x) { tree_node *tmp = new tree_node(x); position._node->children.push_back(tmp); tmp->parent = position._node; return iterator(tmp); } //後序遞迴輸出 void post_recurs_render(tree_node* some, unsigned recurs_level) { for (unsigned i = 0; i < some->children.size(); i++) post_recurs_render(some->children[i], recurs_level+1); for (int i = 0; i<recurs_level; i++) cout << " "; cout << some->name << endl; } //先序遞迴輸出 void pre_recurs_render(tree_node* some, unsigned recurs_level) { for (int i = 0; i<recurs_level; i++) cout << " "; cout << some->name << endl; for (unsigned i = 0; i < some->children.size(); i++) pre_recurs_render(some->children[i], recurs_level+1); } //利用stack //使用Transform格式化輸出 void recurs_render(tree_node* some) { std::string temp; temp = form_stack.top() + some->format; form_stack.push(temp); cout << temp; cout << some->name; cout << endl; for (unsigned i = 0; i < some->children.size(); i++) recurs_render(some->children[i]); form_stack.pop(); } tree_node *root; private: void Init(){ form_stack.push(std::string(" ")); }; void destroy(tree_node *some) { #define SAFE_DELETE(p) {if(p){delete p; p=NULL;}} //後序刪除 for (unsigned i = 0; i < some->children.size(); i++) destroy(some->children[i]); SAFE_DELETE(some); } std::stack<std::string> form_stack; };

下面是main函式裡的測試程式碼：

int main() { //for detecting the memory leaks int tmpFlag = _CrtSetDbgFlag( _CRTDBG_REPORT_FLAG ); tmpFlag |= _CRTDBG_LEAK_CHECK_DF; _CrtSetDbgFlag( tmpFlag ); typedef htree_node<string> node_type; typedef htree<string> tree_type; node_type *one = new node_type("one"); tree_type::iterator iter(one); tree_type tr1(one); tree_type::iterator two = tr1.insert(iter, "two"); tree_type::iterator three = tr1.insert(iter, "three"); tr1.insert(two, "apple"); tr1.insert(two, "banana"); tr1.insert(two, "peach"); tr1.insert(three, "china"); tr1.insert(three, "england"); //method 1： tr1.recurs_render(tr1.root); cout << "--------" << endl; //method 2: tr1.pre_recurs_render(tr1.root, 1); cout << "--------" << endl; //method 3: tr1.post_recurs_render(tr1.root, 1); cout << "--------" << endl; // test iterator::end() function cout << (* (iter.end()) ) << endl; return 0; }

最終輸出結果：

one two apple banana peach three china england -------- one two apple banana peach three china england -------- apple banana peach two china england three one -------- england