[置顶] 数据结构之 二叉树的构造与遍历(先序，中序，后序，层次)

// 二叉树.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>
#define maxSize 10
using namespace std;

typedef struct BinaryTreeNode
{
    char data;
    BinaryTreeNode * leftChild;
    BinaryTreeNode * rightChild;
}Node;
//构造二叉树 使用先序和中序构造一颗二叉树
void MakeBinaryTree(Node** root, char* preOrder, char* midOrder, int length)
{
    if (length == 0)
    {
        (*root) = NULL;
        return;
    }
    (*root) = new Node;
    (*root)->data = *preOrder;

    char * rootplace = strchr(midOrder, (*root)->data);
    if (rootplace == NULL)
    {
        cout <<"input wrong order sample!"<<endl;
    }
    int leftTreeLength = strlen(midOrder) - strlen(rootplace);
    int rightTreeLength = length - leftTreeLength - 1;

    MakeBinaryTree(&(*root)->leftChild, preOrder+1, midOrder, leftTreeLength);
    MakeBinaryTree(&(*root)->rightChild, preOrder+leftTreeLength+1, rootplace+1, rightTreeLength);
}

void PostTraverse(Node* root)
{
    if (root == NULL)
        return;
    PostTraverse(root->leftChild);
    PostTraverse(root->rightChild);
    cout << root->data;
}
void visit(Node *p)
{
	printf("%c ",p->data);
}
//先序遍历
void preOrder(Node *p)
{
	if(p==NULL)
		return;
	visit(p);
	preOrder(p->leftChild);
	preOrder(p->rightChild);
}
//中序遍历
void inOrder(Node *p)
{
	if(p==NULL)
		return;
	inOrder(p->leftChild);
	visit(p);
	inOrder(p->rightChild);
}
//后序遍历
void postOrder(Node *p)
{
	if(p==NULL)
		return;
	postOrder(p->leftChild);
	postOrder(p->rightChild);
	visit(p);
}

//层次遍历
typedef struct
{
	Node *data[maxSize];
	int front;
	int rear;
}SqQueue;
void level(Node *&p)
{
	Node *q;
	SqQueue qu;
	qu.front=qu.rear=0;

	qu.rear=(qu.rear+1)%maxSize;
	qu.data[qu.rear]=p;//进队

	while(qu.front!=qu.rear)
	{
		qu.front=(qu.front+1)%maxSize;
		q=qu.data[qu.front]; //出队

		visit(q);

		if(q->leftChild!=NULL)
		{
			qu.rear=(qu.rear+1)%maxSize;
			qu.data[qu.rear]=q->leftChild;//左孩子进队
		}
		if(q->rightChild!=NULL)
		{
			qu.rear=(qu.rear+1)%maxSize;
			qu.data[qu.rear]=q->rightChild;//右孩子进队
		}
	}
}

int _tmain(int argc, _TCHAR* argv[])
{
	char pre[] = "abdeijcfg";
    char mid[] = "dbiejafcg";	//"bdeijafcg"  "dijebfgca"
    Node* r;
    MakeBinaryTree(&r, pre, mid, strlen(pre));//构造了一颗二叉树
	printf("先序遍历:");
    preOrder(r);
	printf("\n中序遍历:");
    inOrder(r);
	printf("\n后序遍历:");
    postOrder(r);
	printf("\n层次遍历:");
    level(r);
    return 0;
}