二叉树的遍历（先、中、后、层序）C实现

#include<stdio.h>
#include<stdlib.h>
#include<stack>
using namespace std;

typedef struct TreeNode* BiTree;
typedef char ElementType;
struct TreeNode{
ElementType Data;
BiTree Left;
BiTree Right;
};

BiTree CreateTree()
{
ElementType ch;
BiTree T = (BiTree)malloc(sizeof(struct TreeNode));
if(T == NULL){
printf("Over flow");
return NULL;
}
scanf("%c",&ch);
if(ch == '#')
T = NULL;
else{
T->Data = ch;
T->Left = CreateTree();
T->Right = CreateTree();
}
return T;
}

void PreTraversal(BiTree T)//递归版本 先序遍历
{
if(T != NULL){
printf("%c ",T->Data);
PreTraversal(T->Left);
PreTraversal(T->Right);
}
}

void PreTraversalRe(BiTree T)//非递归前序遍历
{
stack<BiTree> S;
while(T != NULL || !S.empty()){
while(T != NULL){
printf("%c ",T->Data);
S.push(T);
T = T->Left;
}
if(!S.empty()){
T = S.top();
S.pop();
T = T->Right;
}
}
}

void InTraversal(BiTree T)//递归版本中序遍历
{
if(T != NULL){
InTraversal(T->Left);
printf("%c ",T->Data);
InTraversal(T->Right);
}
}

void InTraversalRe(BiTree T)//非递归中序遍历
{
stack<BiTree> S;
while(T != NULL || !S.empty()){
while(T != NULL){
S.push(T);
T = T->Left;
}
if(!S.empty()){
T = S.top();
printf("%c ",T->Data);
S.pop();
T = T->Right;
}
}
}

void PostTraversal(BiTree T)//递归版本 后续遍历
{
if(T != NULL){
PreTraversal(T->Left);
PreTraversal(T->Right);
printf("%c ",T->Data);
}
}

void PostTraversalRe(BiTree T) //非递归 后序遍历
{
BiTree Pre = NULL;
stack<BiTree> S;
while(T != NULL || !S.empty()){
while(T != NULL){
S.push(T);
T = T->Left;
}
T = S.top();
if(T->Right == NULL || Pre == T->Right){
printf("%c ",T->Data);
S.pop();
Pre = T;
T = NULL; //为了 继续取栈顶元素
}
else{
T = T->Right;
}
}
}

void LevelOrderTraversal(BiTree T)//层序遍历
{
deque<BiTree> Q;
if(T == NULL)
return;
Q.push_back(T);
while( !Q.empty()){
T = Q.front();
Q.pop_front();
printf("%c ",T->Data);
if(T->Left != NULL)
Q.push_back(T->Left);
if(T->Right != NULL)
Q.push_back(T->Right);
}
}

int main()
{
BiTree BT;
BT = CreateTree();
printf("递归先序遍历 :\n");
PreTraversal(BT);
printf("\n非递归先序遍历 :\n");
PreTraversalRe(BT);
printf("\n递归中序遍历 ：\n");
InTraversal(BT);
printf("\n非递归中序遍历 ：\n");
InTraversalRe(BT);
printf("\n递归后续遍历 :\n");
PostTraversalRe(BT);
printf("\n非递归后续遍历 :\n");
PostTraversalRe(BT);
printf("\n层序遍历 :\n");
LevelOrderTraversal(BT);

return 0;
}