二叉树先序，中序，后序遍历非递归实现

</pre><pre name="code" class="cpp">#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<queue>
#include<stack>
using namespace std;
char in[30],pre[30],last[30];

typedef struct mynode
{
char data;
struct mynode* leftchild;
struct mynode* rightchild;
} Node,*pNode;

void build(char *pre,char *in,int len,pNode &root)
{
if(len<1)
return;
int i=0;
while(pre[0]!=in[i])i++;
root = (pNode)malloc(sizeof(Node));
root->data = pre[0];
root->rightchild = root->leftchild = NULL;
build(pre+1,in,i,root->leftchild);
build(pre+i+1,in+i+1,len-i-1,root->rightchild);
}

//层序遍历
void seqorder(pNode root)
{
pNode temp;
queue<pNode> qe;
qe.push(root);
while(!qe.empty())
{
temp = qe.front();
qe.pop();
printf("%c",temp->data);
if(temp->leftchild)
qe.push(temp->leftchild);
if(temp->rightchild)
qe.push(temp->rightchild);
}
}

//中序遍历
void inorder(pNode root)
{
if(NULL==root) return;
inorder(root->leftchild);
printf("%c",root->data);
inorder(root->rightchild);

}

//前序遍历
void preorder(pNode root)
{
if(NULL==root) return;
printf("%c",root->data);
preorder(root->leftchild);
preorder(root->rightchild);
}

//后续遍历
void lastorder(pNode root)
{
if(NULL==root)return;
lastorder(root->leftchild);
lastorder(root->rightchild);
printf("%c",root->data);
}

//前序非递归
void _preorder(pNode root)
{
stack<pNode> stk;
while(!stk.empty()||root==NULL)
{
while(root)
{
stk.push(root);
printf("%c",root->data);
root = root->leftchild;
}
root = stk.top();
root = root->rightchild;
stk.pop();
}
}
//中序遍历非递归
void _inorder(pNode root)
{
stack<pNode> stk;

while(root||!stk.empty())
{
while(root)
{
stk.push(root);
root = root->leftchild;
}
root = stk.top();
stk.pop();
printf("%c",root->data);
root = root->rightchild;
}
}

//后续遍历非递归
void _lastorder(pNode root)
{
int flag[30];
stack<pNode> stk;
while(root)
{
stk.push(root);
flag[stk.size()] = 0;
root = root->leftchild;
}

while(!stk.empty())
{
root = stk.top();
while(root->rightchild&&flag[stk.size()]==0)
{
flag[stk.size()] = 1;
root = root->rightchild;
while(root)
{
stk.push(root);
flag[stk.size()] = 0;
root = root->leftchild;
}
root = stk.top();
}
printf("%c",root->data);
stk.pop();
}
}
int main(void)
{
scanf("%s %s",pre,in);
pNode root;
build(pre,in,strlen(pre),root);
//lastorder(root);
_lastorder(root);
return 0;
}