二叉树的遍历分为前序遍历，中序遍历，后序遍历，层序遍历，在本文中，前三种由递归实现，层序遍历由队列实现。

#include "stdio.h"
#include "stdlib.h"
#include "windows.h"
typedef struct Node
{char data;struct Node *Left;struct Node *Right;struct Node *Next;
}BT;typedef struct { /* 链队列结构 */BT *rear; /* 指向队尾结点 */BT *front; /* 指向队头结点 */
} LinkQueue;
//入队
LinkQueue* AddQuee(LinkQueue *PtrL,BT* item)
{BT *node;node=PtrL->rear;if (PtrL->front==NULL){BT *q=(BT*)malloc(sizeof(BT));q->Left=item->Left;q->Right=item->Right;q->Next=NULL;q->data=item->data;PtrL->front=q;PtrL->rear=q;return PtrL;}else{BT *q=(BT*)malloc(sizeof(BT));q->Next=NULL;q->Left=item->Left;q->Right=item->Right;q->data=item->data;node->Next=q;PtrL->rear=q;return PtrL;}
}
//出队
BT* DeleteQ ( LinkQueue *PtrQ )
{BT *firstNode;//BT* NodeItem;if (PtrQ->front==NULL){printf("queue is empty");return NULL;}firstNode=PtrQ->front;if (PtrQ->front==PtrQ->rear){PtrQ->front=PtrQ->rear=NULL;}else{PtrQ->front=PtrQ->front->Next;}//NodeItem->data=firstNode->data;//free(firstNode);return firstNode;
}
//判断是否为空
int isempty(LinkQueue *PtrL)
{if (PtrL->rear==NULL){return 1;}else{return 0;}
}BT *CreateBiTree()
{char ch;BT *T;printf("please enter tree node:");scanf("%c",&ch);if (ch=='#'){T=NULL;}else{T=(BT*)malloc(sizeof(BT));T->data=ch;T->Left=CreateBiTree();T->Right=CreateBiTree();}return T;
}//先序遍历
void PreOrderTraversal( BT* tree)
{if (tree){printf("%c ",tree->data);PreOrderTraversal(tree->Left);PreOrderTraversal(tree->Right);}
}//中序遍历
void InOrderTraversal(BT* tree)
{if (tree){PreOrderTraversal(tree->Left);printf("%c ",tree->data);PreOrderTraversal(tree->Right);}
}//后序遍历
void PostOderTraversal(BT *tree)
{if (tree){PostOderTraversal(tree->Left);PostOderTraversal(tree->Right);printf("%c ",tree->data);}
}
//层序遍历
void LevelOrderTraversal(BT *tree)
{BT *bt;LinkQueue *q=(LinkQueue*)malloc(sizeof(LinkQueue));q->front=NULL;q->rear=NULL;if (!tree){return;}AddQuee(q,tree);while(isempty(q)==0){bt=DeleteQ(q);printf("%c ",bt->data);if (bt->Left) AddQuee(q,bt->Left);if (bt->Right) AddQuee(q,bt->Right);}}int PostOrderGetHeight( BT* tree )
{int HL, HR, MaxH;if( tree ) {HL = PostOrderGetHeight(tree->Left); /*求左子树的深度*/HR = PostOrderGetHeight(tree->Right); /*求右子树的深度*/MaxH =(HL> HR)? HL : HR;/*取左右子树较大的深度*/return ( MaxH + 1 ); /*返回树的深度*/}else return 0; /* 空树深度为0 */
}void main()
{BT *t;int a;t=CreateBiTree();printf("\n1.PreOrderTraversal\n");printf("2.MidOrderTraversal\n");printf("3.PostOrderTraversal\n");printf("4.EXIT\n");printf("5.LevelOrderTraversal\n");printf("6.show the hieght of the tree");while (1){printf("please enter your order:");scanf("%d",&a);switch (a){case 1:PreOrderTraversal(t);break;case 2:InOrderTraversal(t);break;case 3:PostOderTraversal(t);break;case 4:exit(0);break;case 5:LevelOrderTraversal(t);break;case 6:printf("%d",PostOrderGetHeight(t));break;default:break;}}
}

运行结果

C++实现二叉树的遍历

#include "iostream"
#include "stack"
#include "queue"using namespace std;//二叉树结点
typedef struct BiTNode{//数据char data;//左右孩子指针struct BiTNode *lchild,*rchild;
}BiTNode,*BiTree;//按先序序列创建二叉树
int CreateBiTree(BiTree &T){char data;//按先序次序输入二叉树中结点的值（一个字符），‘#’表示空树scanf("%c",&data);if(data == '#'){T = NULL;}else{T = (BiTree)malloc(sizeof(BiTNode));//生成根结点T->data = data;//构造左子树CreateBiTree(T->lchild);//构造右子树CreateBiTree(T->rchild);}return 0;
}
//输出
void Visit(BiTree T){if(T->data != '#'){printf("%c ",T->data);}
}
//先序遍历
void PreOrder(BiTree T){if(T != NULL){//访问根节点Visit(T);//访问左子结点PreOrder(T->lchild);//访问右子结点PreOrder(T->rchild);}
}
//中序遍历  
void InOrder(BiTree T){  if(T != NULL){  //访问左子结点  InOrder(T->lchild);  //访问根节点  Visit(T);  //访问右子结点  InOrder(T->rchild);  }  
}  
//后序遍历
void PostOrder(BiTree T){if(T != NULL){//访问左子结点PostOrder(T->lchild);//访问右子结点PostOrder(T->rchild);//访问根节点Visit(T);}
}
/* 先序遍历(非递归)思路：访问T->data后，将T入栈，遍历左子树；遍历完左子树返回时，栈顶元素应为T，出栈，再先序遍历T的右子树。
*/
void PreOrder2(BiTree T){stack<BiTree> stack;//p是遍历指针BiTree p = T;//栈不空或者p不空时循环while(p || !stack.empty()){if(p != NULL){//存入栈中stack.push(p);//访问根节点printf("%c ",p->data);//遍历左子树p = p->lchild;}else{//退栈p = stack.top();stack.pop();//访问右子树p = p->rchild;}}//while
}
/* 中序遍历(非递归)思路：T是要遍历树的根指针，中序遍历要求在遍历完左子树后，访问根，再遍历右子树。先将T入栈，遍历左子树；遍历完左子树返回时，栈顶元素应为T，出栈，访问T->data，再中序遍历T的右子树。
*/
void InOrder2(BiTree T){stack<BiTree> stack;//p是遍历指针BiTree p = T;//栈不空或者p不空时循环while(p || !stack.empty()){if(p != NULL){//存入栈中stack.push(p);//遍历左子树p = p->lchild;}else{//退栈，访问根节点p = stack.top();printf("%c ",p->data);stack.pop();//访问右子树p = p->rchild;}}//while
}//后序遍历(非递归)
typedef struct BiTNodePost{BiTree biTree;char tag;
}BiTNodePost,*BiTreePost;void PostOrder2(BiTree T){stack<BiTreePost> stack;//p是遍历指针BiTree p = T;BiTreePost BT;//栈不空或者p不空时循环while(p != NULL || !stack.empty()){//遍历左子树while(p != NULL){BT = (BiTreePost)malloc(sizeof(BiTNodePost));BT->biTree = p;//访问过左子树BT->tag = 'L';stack.push(BT);p = p->lchild;}//左右子树访问完毕访问根节点while(!stack.empty() && (stack.top())->tag == 'R'){BT = stack.top();//退栈stack.pop();BT->biTree;printf("%c ",BT->biTree->data);}//遍历右子树if(!stack.empty()){BT = stack.top();//访问过右子树BT->tag = 'R';p = BT->biTree;p = p->rchild;}}//while
}
//层次遍历
void LevelOrder(BiTree T){BiTree p = T;//队列queue<BiTree> queue;//根节点入队queue.push(p);//队列不空循环while(!queue.empty()){//对头元素出队p = queue.front();//访问p指向的结点printf("%c ",p->data);//退出队列queue.pop();//左子树不空，将左子树入队if(p->lchild != NULL){queue.push(p->lchild);}//右子树不空，将右子树入队if(p->rchild != NULL){queue.push(p->rchild);}}
}
int main()
{BiTree T;CreateBiTree(T);printf("先序遍历：\n");PreOrder(T);printf("\n");printf("先序遍历(非递归)：\n");PreOrder2(T);printf("\n");printf("中序遍历：\n");InOrder(T);printf("\n");printf("中序遍历(非递归)：\n");InOrder2(T);printf("\n");printf("后序遍历：\n");PostOrder(T);printf("\n");printf("后序遍历(非递归)：\n");PostOrder2(T);printf("\n");printf("层次遍历：\n");LevelOrder(T);printf("\n");system("pause");return 0;
}