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二叉樹是一種非線性結(jié)構(gòu),遍歷二叉樹幾乎都是通過遞歸或者用棧輔助實現(xiàn)非遞歸的遍歷。用二叉樹作為存儲結(jié)構(gòu)時,取到一個節(jié)點,只能獲取節(jié)點的左孩子和右孩子,不能直接得到節(jié)點的任一遍歷序列的前驅(qū)或者后繼。
而線索二叉樹利用二叉樹中指向左右子樹的空指針來存放節(jié)點的前驅(qū)和后繼信息
結(jié)點信息如下
enum PointerTag{ THREAD, LINK }; template<class T> struct BinaryTreeNodeThd { T _data; //數(shù)據(jù) BinaryTreeNodeThd<T>* _left; //左孩子 BinaryTreeNodeThd<T>* _right; //右孩子 PointerTag _leftTag; //左孩子線索標(biāo)志 PointerTag _rightTag; //右孩子線索標(biāo)志 };
其前序結(jié)構(gòu)如下
其中序結(jié)構(gòu)如下
程序?qū)崿F(xiàn):
#include<iostream> using namespace std; enum PointerTag{ THREAD, LINK }; template<class T> struct BinaryTreeNodeThd { T _data; //數(shù)據(jù) BinaryTreeNodeThd<T>* _left; //左孩子 BinaryTreeNodeThd<T>* _right; //右孩子 PointerTag _leftTag; //左孩子線索標(biāo)志 PointerTag _rightTag; //右孩子線索標(biāo)志 BinaryTreeNodeThd(const T& x) :_data(x) , _left(NULL) , _right(NULL) , _leftTag(LINK) , _rightTag(LINK) {} }; template<class T> class BinaryTreeThd { typedef BinaryTreeNodeThd<T> Node; public: BinaryTreeThd() :_root(NULL) {} BinaryTreeThd(const T*a, size_t size, const T& invalid) { size_t index = 0; _root = _CreateTree(a, size, index, invalid); } void InOrderThreading()//中序線索化 { Node*prev = NULL; _InOrderThreading(_root, prev); } void PrevOderThreading()//前序線索化 { Node*prev = NULL; _PrevOderThreading(_root, prev); } void InOrderThd()//中序遍歷 { _InOrderThd(_root); } void PrevOrderThd()//前序遍歷 { _PrevOrderThd(_root); } protected: Node* _CreateTree(const T*a, size_t size, size_t& index, const T& invalid) { Node* _root = NULL; if (index < size&&a[index] != invalid) { _root = new Node(a[index]); _root->_left = _CreateTree(a, size, ++index, invalid); _root->_right = _CreateTree(a, size, ++index, invalid); } return _root; } void _PrevOderThreading(Node* root, Node*& prev)//前序線索化 { if (root == NULL) return; if (root->_left == NULL) { root->_leftTag = THREAD; root->_left = prev; } if (prev&&prev->_right == NULL) { prev->_rightTag = THREAD; prev->_right = root; } prev = root; if (root->_leftTag == LINK)//遞歸 { _PrevOderThreading(root->_left,prev);//線索化左子樹 } if (root->_rightTag == LINK) { _PrevOderThreading(root->_right,prev);//線索化右子樹 } } void _PrevOrderThd(Node* root) { Node*cur = root; while (cur) { while (cur->_leftTag == LINK) { cout << cur->_data << " "; cur = cur->_left; } cout << cur->_data << " "; cur = cur->_right; } } /*方法二 void _PrevOrderThd(Node* root) { Node*cur = root; while (cur) { while (cur->_leftTag==LINK) { cout << cur->_data << " "; cur = cur->_left; } cout << cur->_data << " "; while (cur->_rightTag == THREAD) { cur = cur->_right; cout << cur->_data << " "; } if (cur->_leftTag == LINK) { cur = cur->_left; } else { cur = cur->_right; } } }*/ void _InOrderThreading(Node* _root, Node* &prev)//中序線索化 { if (_root == NULL) { return; } if (_root->_leftTag==LINK) _InOrderThreading(_root->_left,prev); //線索化 if (_root->_left == NULL)//左孩子為空 { _root->_leftTag = THREAD; _root->_left = prev; } if (prev != NULL&&prev->_right == NULL)//前驅(qū)的右孩子為空 { prev->_rightTag = THREAD; prev->_right = _root; } prev = _root; if (_root->_rightTag==LINK)//線索化右孩子 _InOrderThreading(_root->_right,prev); } void _InOrderThd(Node* _root) //中序遍歷 { Node* cur = _root; while (cur) { while (cur->_leftTag == LINK) { cur = cur->_left; } cout << cur->_data << " "; while (cur->_rightTag == THREAD) { cur = cur->_right; cout << cur->_data << " "; } cur = cur->_right; } cout << endl; } protected: Node* _root; };
測試
int main() { int a1[10] = { 1, 2, 3, '#', '#', 4, '#', '#', 5, 6 }; BinaryTreeThd<int> t1(a1, 10, '#'); cout << endl << "中序遍歷:"; t1.InOrderThreading(); t1.InOrderThd(); cout << "前序遍歷" << endl; BinaryTreeThd<int>t2(a1, 10, '#'); t2.PrevOderThreading(); t2.PrevOrderThd(); getchar(); return 0; }
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