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

typedef struct BiTree
{
    char data;
    struct BiTree * pLchild;
    struct BiTree * pRchild;

}BITREE,* PBT;

PBT createBiTree(void)
{
    PBT pBTa = (PBT)malloc(sizeof(BITREE));
    PBT pBTb = (PBT)malloc(sizeof(BITREE));
    PBT pBTc = (PBT)malloc(sizeof(BITREE));
    PBT pBTd = (PBT)malloc(sizeof(BITREE));
    PBT pBTe = (PBT)malloc(sizeof(BITREE));
    PBT pBTf = (PBT)malloc(sizeof(BITREE));
    PBT pBTg = (PBT)malloc(sizeof(BITREE));

    pBTa->data = 'A';
    pBTb->data = 'B';
    pBTc->data = 'C';
    pBTd->data = 'D';
    pBTe->data = 'E';
    pBTf->data = 'F';
    pBTg->data = 'G';

    pBTa->pLchild = pBTc;
    pBTa->pRchild = pBTb;
    pBTc->pLchild = NULL;
    pBTc->pRchild = pBTd;
    pBTd->pLchild = pBTd->pRchild = NULL;
    pBTb->pLchild = pBTe;
    pBTb->pRchild = pBTf;
    pBTe->pLchild = NULL;
    pBTe->pRchild = pBTg;
    pBTf->pLchild = pBTf->pRchild = NULL;

    return pBTa;
}

void preTraverse(PBT pBT)
{
    if(pBT != NULL)
    {
        printf("%c\n",pBT->data);

        if (pBT->pLchild != NULL)
        {
            preTraverse(pBT->pLchild);
        }
        if (pBT->pRchild != NULL)
        {
            preTraverse(pBT->pRchild);
        }
    }
    return;
}

int main(void)
{
    PBT pBT = createBiTree();
    preTraverse(pBT);
    return 0;
}

是的，我漏了一句：pBTg->pLchild = pBTg->pRchild = NULL; 加上去就好了。这个二叉树是我自己随便编的，G是叶子节点，是我漏了一句。谢谢版主!

不过，没有这一句，我这里不能输出的，结果就是P和？，而不是正常结果后边带了一堆P和？  

见图片

明白了，谢谢