题目要求:
实现二叉搜索树的前序、中序、后序非递归遍历。
题目分析:
非递归前序遍历:使用一个辅助栈,出栈一个结点并输出该结点,同时依次入栈该结点的右结点和左结点,再出栈,入栈...;
非递归中序遍历:使用一个辅助栈和一个临时结点,临时结点不断找树的左子树,知道为空,然后又跳到空结点父结点的右子树,又继续找右子树的左子树;
非递归后序遍历:使用两个辅助栈。
代码实现:
#include <iostream> #include <stack> using namespace std; typedef struct BinaryTree { struct BinaryTree *left,*right; int data; }BinaryTree; void initTree(BinaryTree **p); void PreOrderTree(BinaryTree *p); void InOrderTree(BinaryTree *p); void PostOrderTreeTraversal(BinaryTree *p); int main(void) { BinaryTree *root; initTree(&root); PreOrderTree(root); InOrderTree(root); PostOrderTreeTraversal(root); return 0; } void PreOrderTree(BinaryTree *p) { stack<BinaryTree *> s; s.push(p); cout << "二叉搜索树的非递归前序遍历为:"; while(!s.empty()) { BinaryTree *tmp = s.top(); cout << tmp->data << " "; s.pop(); if(tmp->right) s.push(tmp->right); if(tmp->left) s.push(tmp->left); } cout << endl; } void InOrderTree(BinaryTree *p) { stack<BinaryTree *> s; BinaryTree *cur = p; cout << "二叉搜索树的非递归中序遍历为:"; while(!s.empty() || cur!=NULL) { if(cur!=NULL) { s.push(cur); cur = cur->left; } else { cur = s.top(); s.pop(); cout << cur->data << " "; cur = cur->right; } } cout << endl; } void PostOrderTreeTraversal(BinaryTree *p) { stack<BinaryTree *> sTraversal,sVisit; sTraversal.push(p); while(!sTraversal.empty()) { BinaryTree *tmp = sTraversal.top(); sTraversal.pop(); sVisit.push(tmp); if(tmp->left) sTraversal.push(tmp->left); if(tmp->right) sTraversal.push(tmp->right); } cout << "二叉搜索树的非递归后序遍历:"; while(!sVisit.empty()) { cout << sVisit.top()->data << " "; sVisit.pop(); } cout << endl; } // 10 // / // 5 12 // / // 4 7 void initTree(BinaryTree **p) { *p = new BinaryTree; (*p)->data = 10; BinaryTree *tmpNode = new BinaryTree; tmpNode->data = 5; (*p)->left = tmpNode; tmpNode = new BinaryTree; tmpNode->data = 12; (*p)->right = tmpNode; tmpNode->left = NULL; tmpNode->right = NULL; BinaryTree *currentNode = (*p)->left; tmpNode = new BinaryTree; tmpNode->data = 4; currentNode->left = tmpNode; tmpNode->left = NULL; tmpNode->right = NULL; tmpNode = new BinaryTree; tmpNode->data = 7; currentNode->right = tmpNode; tmpNode->left = NULL; tmpNode->right = NULL; cout << "二叉搜索树为:" <<endl; cout << " " << 10<<endl; cout << " " <<"/" << " "<< "\" <<endl; cout << " " << 5 << " " << 12 << endl; cout << " " <<"/" << " "<< "\" <<endl; cout << 4 << " " << 7 << endl; }