二叉树的前序遍历是：根结点、左结点、右结点

假设我们要构造的二叉树是：前序遍历ABDCE，因程序中要知道叶子结点，扩展后为AB#D##C#E##

代码如下图所示： 

#include 
     
      #include 
      
       //二叉树的结构typedef struct tree *BinTree;struct tree{    char data;    BinTree left;    BinTree right;};//前序遍历递归构造二叉树BinTree BuildBinTree(){    char data;    BinTree root;    scanf("%c",&data);        if (data == '#'){        root = NULL;     }    else    {        root = (BinTree)malloc(sizeof(struct tree));        root->data = data;        root->left = BuildBinTree();        root->right = BuildBinTree();    }    return root;}//前序遍历进行验证void PreTraversalTree(BinTree root){    if (root != NULL)    {        printf("%c",root->data);        PreTraversalTree(root->left);        PreTraversalTree(root->right);    }}int main(){    BinTree root;    printf("create Binary Tree\n");    root = BuildBinTree();    printf("\n");    PreTraversalTree(root);    system("pause");    return 0;}
      
     

输出结果：