二叉树（C语言实现）

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

struct BTNode
{
    char data;
    struct BTNode * pLchild; //p是指针 L是左  child是孩子
    struct BTNode * pRchild;
};

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

int main(void)
{
    struct BTNode * pT = CreateBTree();
    
//    PreTraverseBTree(pT);
//    InTraverseBTree(pT);
    PostTraverseBTree(pT);
    
    return 0;
}

void PostTraverseBTree(struct BTNode * pT)
{
    if (NULL != pT)
    {
        if (NULL != pT->pLchild)
        {
            PostTraverseBTree(pT->pLchild);
        }    
        if (NULL != pT->pRchild)
        {
                PostTraverseBTree(pT->pRchild);
            //pT->pLchild可以代表整个左子树
        }
        printf("%c
", pT->data);
    }
}

void InTraverseBTree(struct BTNode * pT)
{
    if (NULL != pT)
    {
        if (NULL != pT->pLchild)
        {
            InTraverseBTree(pT->pLchild);
        }
        
        printf("%c
", pT->data);
    
        if (NULL != pT->pRchild)
        {
                InTraverseBTree(pT->pRchild);
            //pT->pLchild可以代表整个左子树
        }    
    }
}

void PreTraverseBTree(struct BTNode * pT)
{
    if (NULL != pT)
    {
        printf("%c
", pT->data);
    
        if (NULL != pT->pLchild)
        {
            PreTraverseBTree(pT->pLchild);
        }
        
        if (NULL != pT->pRchild)
        {
                PreTraverseBTree(pT->pRchild);
            //pT->pLchild可以代表整个左子树
        }    
    }    

/*
    伪算法
    先访问根节点
    再先序访问左子树
    再先序访问右子树
*/
}

struct BTNode * CreateBTree(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->pLchild = NULL;
    pD->pRchild = pE;
    pE->pLchild = pE->pRchild = NULL;

    return pA;
}