二叉树遍历的非递归实现

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55

#include<stdio.h> #include<stack> #include<stdlib.h> using namespace std;   struct ListNode {     int data;     ListNode *lchild,*rchild; };   ListNode* Createbst() {     int data;     scanf("%d",&data);     if(data!=-1)     {         ListNode* root=(ListNode*)malloc(sizeof(ListNode));         root->lchild=root->rchild=NULL;         root->data=data;         root->lchild=Createbst();         root->rchild=Createbst();         return root;     }     else return NULL; }   void PreOrder(ListNode *root) {     stack<ListNode*> s;     ListNode *p=root;     while(p!=NULL || !s.empty())     {         while(p!=NULL)         {             printf("%d",p->data);             s.push(p);             p=p->lchild;         }         if(!s.empty())         {             p=s.top();             s.pop();             p=p->rchild;         }     } }   int main() {     ListNode* root;     root=Createbst();     PreOrder(root);     return 0; }

　中序遍历

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

void InOrder(ListNode*root) {     stack<ListNode*>s;     ListNode* p=root;     while(p!=NULL || !s.empty())     {         while(p!=NULL)         {             s.push(p);             p=p->lchild;         }         if(!s.empty())         {             p=s.top();             s.pop();             printf("%d",p->data);             p=p->rchild;         }     } }

　后序遍历

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

struct BiTree {     ListNode* treeNode;     int flag; }; void PostOrder(ListNode* root) {    stack<BiTree*> s;    BiTree* sTree=(BiTree*)malloc(sizeof(BiTree));    sTree->treeNode=root;    sTree->flag=0;    s.push(sTree);    while(!s.empty())    {        BiTree* tmptree=s.top();        if(tmptree->flag==2)        {            printf("%d ",tmptree->treeNode->data);            s.pop();        }        else        {            if(tmptree->treeNode->rchild)            {                sTree=(BiTree*)malloc(sizeof(BiTree));                sTree->flag=0;                sTree->treeNode=tmptree->treeNode->rchild;                s.push(sTree);            }            tmptree->flag++;            if(tmptree->treeNode->lchild)            {                sTree=(BiTree*)malloc(sizeof(BiTree));                sTree->flag=0;                sTree->treeNode=tmptree->treeNode->lchild;                s.push(sTree);            }            tmptree->flag++;        }    } }