二叉树几种遍历算法

<span style="font-size:14px;">/*二叉树的遍历*/

#include <iostream>
#include <cstring>
#include <stack>
using namespace std;

typedef struct node
{
char data;
struct node *lchild,*rchild;
}BinTree;

typedef struct node1
{
BinTree *btnode;
bool isFirst;
}BTNode;

void creatBinTree1(BinTree* &root) //前序遍历创建树，形如 A,B,C,#,#,D,#,#,E,#,#
{
char value;
cin>>value;
if(value == '#') root = NULL; //递归结束条件
else
{
root = (BinTree *)malloc(sizeof(BinTree));
root->data = value;
creatBinTree1(root->lchild);
creatBinTree1(root->rchild);
}
}

void creatBinTree2(char *s,BinTree *&root)  //创建二叉树，s为形如A(B,C(D,E))形式的字符串
{
int i;
bool isRight=false;
stack<BinTree*> s1;          //存放结点
stack<char> s2;              //存放分隔符
BinTree *p,*temp;
root->data=s[0];
root->lchild=NULL;
root->rchild=NULL;
s1.push(root);
i=1;
while(i<strlen(s))
{
if(s[i]=='(')
{
s2.push(s[i]);
isRight=false;
}
else if(s[i]==',')
{
isRight=true;
}
else if(s[i]==')')
{
s1.pop();
s2.pop();
}
else if(isalpha(s[i]))
{
p=(BinTree *)malloc(sizeof(BinTree));
p->data=s[i];
p->lchild=NULL;
p->rchild=NULL;
temp=s1.top();
if(isRight==true)
{
temp->rchild=p;
cout<<temp->data<<"的右孩子是"<<s[i]<<endl;
}
else
{
temp->lchild=p;
cout<<temp->data<<"的左孩子是"<<s[i]<<endl;
}
if(s[i+1]=='(')
s1.push(p);
}
i++;
}
}

void display(BinTree *root)        //显示树形结构
{
if(root!=NULL)
{
cout<<root->data;
if(root->lchild!=NULL)
{
cout<<'(';
display(root->lchild);
}
if(root->rchild!=NULL)
{
cout<<',';
display(root->rchild);
cout<<')';
}
}
}

void preOrder1(BinTree *root)     //递归前序遍历
{
if(root!=NULL)
{
cout<<root->data<<" ";
preOrder1(root->lchild);
preOrder1(root->rchild);
}
}

void inOrder1(BinTree *root)      //递归中序遍历
{
if(root!=NULL)
{
inOrder1(root->lchild);
cout<<root->data<<" ";
inOrder1(root->rchild);
}
}

void postOrder1(BinTree *root)    //递归后序遍历
{
if(root!=NULL)
{
postOrder1(root->lchild);
postOrder1(root->rchild);
cout<<root->data<<" ";
}
}

void preOrder2(BinTree *root)     //非递归前序遍历
{
stack<BinTree*> s;
BinTree *p=root;
while(p!=NULL||!s.empty())
{
while(p!=NULL)
{
cout<<p->data<<" ";
s.push(p);
p=p->lchild;
}
if(!s.empty())
{
p=s.top();
s.pop();
p=p->rchild;
}
}
}

void inOrder2(BinTree *root)      //非递归中序遍历
{
stack<BinTree*> s;
BinTree *p=root;
while(p!=NULL||!s.empty())
{
while(p!=NULL)
{
s.push(p);
p=p->lchild;
}
if(!s.empty())
{
p=s.top();
cout<<p->data<<" ";
s.pop();
p=p->rchild;
}
}
}

void postOrder2(BinTree *root)    //非递归后序遍历
{
stack<BTNode*> s;
BinTree *p=root;
BTNode *temp;
while(p!=NULL||!s.empty())
{
while(p!=NULL)              //沿左子树一直往下搜索，直至出现没有左子树的结点
{
BTNode *btn=(BTNode *)malloc(sizeof(BTNode));
btn->btnode=p;
btn->isFirst=true;
s.push(btn);
p=p->lchild;
}
if(!s.empty())
{
temp=s.top();
s.pop();
if(temp->isFirst==true)     //表示是第一次出现在栈顶
{
temp->isFirst=false;
s.push(temp);
p=temp->btnode->rchild;
}
else                        //第二次出现在栈顶
{
cout<<temp->btnode->data<<" ";
p=NULL;
}
}
}
}

void postOrder3(BinTree *root)     //非递归后序遍历
{
stack<BinTree*> s;
BinTree *cur;                      //当前结点
BinTree *pre=NULL;                 //前一次访问的结点
s.push(root);
while(!s.empty())
{
cur=s.top();
if((cur->lchild==NULL&&cur->rchild==NULL)||
(pre!=NULL&&(pre==cur->lchild||pre==cur->rchild)))
{
cout<<cur->data<<" ";  //如果当前结点没有孩子结点或者孩子节点都已被访问过
s.pop();
pre=cur;
}
else
{
if(cur->rchild!=NULL)
s.push(cur->rchild);
if(cur->lchild!=NULL)
s.push(cur->lchild);
}
}
}

int main(int argc, char *argv[])
{
char s[100];
while(scanf("%s",s)==1)
{
BinTree *root=(BinTree *)malloc(sizeof(BinTree));
creatBinTree2(s,root);
display(root);
cout<<endl;
preOrder2(root);
cout<<endl;
inOrder2(root);
cout<<endl;
postOrder2(root);
cout<<endl;
postOrder3(root);
cout<<endl;
}
return 0;
}
</span>