学步园

#include<stdio.h>
#include<stdlib.h>

struct BTNode
{
    int data;
    struct BTNode *pLchild;//左子树
    struct BTNode *pRchild;//右子树
};

void PreTraverseBTree(struct BTNode *pT);
void InTraverseBTree(struct BTNode *pT);
void PostTraverseBTree(struct BTNode *pT);
struct BTNode *CreatBTree();
int main()
{
    struct BTNode *pT = CreatBTree();
    PreTraverseBTree(pT);//先序
    printf("\b.\n");
    InTraverseBTree(pT);//中序
    printf("\b.\n");
    PostTraverseBTree(pT);//后序
    printf("\b.\n");
    return 0;
}

void PreTraverseBTree(struct BTNode *pT)
{
    /*先访问根结点
      再先序访问左子树
      再先序访问右子树
    */
    if(NULL != pT)
    {
        printf("%c,",pT->data);
        if(NULL != pT->pLchild)
        {
            PreTraverseBTree(pT->pLchild);
        }
        if(NULL != pT->pRchild)
        {
            PreTraverseBTree(pT->pRchild);
        }
    }

}

void InTraverseBTree(struct BTNode *pT)
{
    /*先中序访问左子树
      再访问根结点
      再中序访问右子树
    */
    if(NULL != pT)
    {
        if(NULL != pT->pLchild)
        {
            InTraverseBTree(pT->pLchild);
        }
        printf("%c,",pT->data);
        if(NULL != pT->pRchild)
        {
            InTraverseBTree(pT->pRchild);
        }
    }

}

void PostTraverseBTree(struct BTNode *pT)
{
    /*先后序访问左子树
      再后序访问右子树
      再访问根结点
    */
    if(NULL != pT)
    {
        if(NULL != pT->pLchild)
        {
            PostTraverseBTree(pT->pLchild);
        }

        if(NULL != pT->pRchild)
        {
            PostTraverseBTree(pT->pRchild);
        }
        printf("%c,",pT->data);
    }
}
struct BTNode *CreatBTree()
{
    struct BTNode *pA = (struct BTNode *)malloc(sizeof(struct BTNode));
    struct BTNode *pB = (struct BTNode *)malloc(sizeof(struct BTNode));
    struct BTNode *pC = (struct BTNode *)malloc(sizeof(struct BTNode));
    struct BTNode *pD = (struct BTNode *)malloc(sizeof(struct BTNode));
    struct BTNode *pE = (struct BTNode *)malloc(sizeof(struct BTNode));
    pA->data = 'A';
    pB->data = 'B';
    pC->data = 'C';
    pD->data = 'D';
    pE->data = 'E';
    pA->pLchild = pB;
    pA->pRchild = pC;
    pB->pLchild = pB->pRchild = NULL;
    pC->pLchild = pD;
    pC->pRchild = NULL;
    pD->pLchild = NULL;
    pD->pRchild = pE;
    pE->pLchild = pE->pRchild = NULL;

    return pA;
}