先宣告一個結構體：二叉樹的三個元素，資料域，左子樹，右子樹。

typedef char ElemType;
typedef struct Node 
{
    ElemType data;
    struct Node *lchild,*rchild;
}BitTree;

BitTree *createBinTreeByPreIn(char
 
 *pre,char *in,int number)
{
    if(number==0)  return NULL;
    char c = pre[0];
    int i = 0;
    while(i<number && in[i]!=c)i++;
    int leftNumber = i;
    int rightNumber = number - i - 1;
    BitTree *node = (BitTree *)malloc(sizeof(BitTree));
    node->data = c;
    node->lchild = createBinTreeByPreIn(&pre[1
 
],&in[0],leftNumber);
    node->rchild = createBinTreeByPreIn(&pre[leftNumber+1],&in[leftNumber+1],rightNumber);
    return node;
}

最後主函式測試一下：

int main(int argc,char **argv)
{
    char a[SIZE],b[SIZE];
    BitTree *p;
    while(scanf("%s%s",a,b)!=EOF)
    {
        p = createBinTreeByPreIn(a,b,strlen(a));
        printf(
 
"\n");
    }
    return 0;
}