链式二叉树的具体程序 郝斌老师-数据结构

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#include<stdio.h>
#include<malloc.h>

struct BTNode *CreatBiTree();
void PreTraverseBTree(struct BTNode *pT);
void InTraverseBTree(struct BTNode *pT);
void PostTraverseBTree(struct BTNode *pT);

struct BTNode
{
    int data;
    struct BTNode *pLchild;//p是指针，L是左，child是孩子；
    struct BTNode *pRchild;
};
int main(void)
{
    BTNode *pT = CreatBiTree();
    printf("先序遍历是：");
    PreTraverseBTree(pT);//先序遍历
    printf("\n");

    printf("中序遍历是：");
    InTraverseBTree(pT);//中序遍历
    printf("\n");

    printf("后序遍历是：");
    PostTraverseBTree(pT);//后序遍历
    printf("\n");

    return 0;
}
struct BTNode *CreatBiTree(void)
{
    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->pRchild = pE;
    pD->pLchild = NULL;
    pE->pLchild = pE->pRchild = NULL;

    return pA;//返回根节点的地址，将A的地址赋给pT，创造根节点
}

void PreTraverseBTree(struct BTNode *pT)
{/*伪算法
    先访问根节点
    在先序访问左子树
    再先序访问右子树*/

    if (pT != NULL)//若是不加if判断，结果会出错
    {
        printf("%c ", pT->data);
        //pT->pLchild可以代表整个左子树
        if (NULL != pT->pLchild)
        {
            PreTraverseBTree(pT->pLchild);
        }
        if (NULL != pT->pRchild)
        {
            PreTraverseBTree(pT->pRchild);
        }
    }

}
void InTraverseBTree(struct BTNode *pT)
{
    if (pT != NULL)//若是不加if判断，结果会出错
    {
        //pT->pLchild可以代表整个左子树
        if (NULL != pT->pLchild)
        {
            InTraverseBTree(pT->pLchild);
        }
        printf("%c ", pT->data);

        if (NULL != pT->pRchild)
        {
            InTraverseBTree(pT->pRchild);
        }
    }
}

void PostTraverseBTree(struct BTNode *pT)
{
    if (pT != NULL)//若是不加if判断，结果会出错
    {

        //pT->pLchild可以代表整个左子树
        if (NULL != pT->pLchild)
        {
            PostTraverseBTree(pT->pLchild);
        }

        if (NULL != pT->pRchild)
        {
            PostTraverseBTree(pT->pRchild);
        }
        printf("%c ", pT->data);
    }
}