非递归实现树的遍历

【代码】

#include <iostream>#include <stack>using namespace std;typedef struct Node{char key;struct Node *lchild, *rchild;}*Tree, TNode;void PreOrder(Tree T) //先序遍历{if (T == NULL)return;TNode *curr = T;//TNode *tmp;stack<Tree> s;while (curr != NULL || !s.empty()) {if (curr != NULL) {cout<<curr->key;s.push(curr);curr = curr->lchild;}else {curr = s.top();s.pop();curr = curr->rchild;}}/*while (curr != NULL) {cout<<curr->key;s.push(curr);curr = curr->lchild;}while(!s.empty()) {curr = s.top();s.pop();tmp = curr->rchild;while(tmp != NULL) {cout<<tmp->key;s.push(tmp);tmp = tmp->lchild;}}*/}void InOrder(Tree T)  //中序遍历{if (T == NULL)return;TNode *curr = T;//TNode *tmp;stack<Tree> s;while ((curr != NULL) || !s.empty()) {if (curr != NULL) {s.push(curr);curr = curr->lchild;}else {curr = s.top();cout<<curr->key;s.pop();curr = curr->rchild;}}}void PostOrder(Tree T) //后序遍历{if (T == NULL)return ;TNode *curr = T, *pre = NULL;stack<Tree> s;while (curr != NULL || !s.empty()) {if (curr != NULL) {s.push(curr);curr = curr->lchild;}else {curr = s.top();s.pop();if (curr->rchild != NULL && curr->rchild != pre) {s.push(curr);curr = curr->rchild;}else {cout<<curr->key;pre = curr;curr = NULL;}}}}Tree createTree(char *s, int n, int i) //建树{if (i >= n)return NULL;TNode *curr;curr = (TNode *)malloc(sizeof(TNode));curr->key = s[i];curr->lchild = createTree(s, n, 2*(i+1)-1);curr->rchild = createTree(s, n, 2*(i+1));return curr;}void freeTree(Tree T)  //释放{if (T != NULL){freeTree(T->lchild);freeTree(T->rchild);delete T;}}int main(void){char s[] = "ABCDEFG";Tree T;T = createTree(s, 7, 0);InOrder(T);cout<<endl;PreOrder(T);cout<<endl;PostOrder(T);cout<<endl;freeTree(T);return 0;}