二叉树的前中后序遍历

typedef struct TreeNode{
    struct TreeNode *left;
    struct TreeNode *right;
    char val;
}BiTreeNode, *binTree;

// 按照前序遍历的方式输入，遇到没有左孩子和右孩子用空格代替
void createTree_(binTree *root){
    char input;
    scanf("%c", &input);
    if (input == ' ') {
        root = NULL;
        return;
    }
    *root = (struct TreeNode *)malloc(sizeof(struct TreeNode));
    (*root)->val = input;
    createTree_(&(*root)->left);
    createTree_(&(*root)->right);
}


// 前序遍历
void PreOrderTraversalBinTree(BiTreeNode *root){
    if (root == NULL) {  return;  }
    printf("%c", root->val);
    PreOrderTraversalBinTree(root->left);
    PreOrderTraversalBinTree(root->right);
}

// 中序遍历
void InOrderTraversalBinTree(BiTreeNode *root){
    if (root == NULL) { return;  }
    InOrderTraversalBinTree(root->left);
    printf("%c", root->val);
    InOrderTraversalBinTree(root->right);
    
}
//后序遍历
void TailOrderTraversalBinTree(BiTreeNode *root){
    if (root == NULL) { return;  }
    TailOrderTraversalBinTree(root->left);
    TailOrderTraversalBinTree(root->right);
    printf("%c", root->val);
}

+ (void)test{
    printf("请按照前序遍历方式输入二叉树：");
    binTree root = NULL;
    createTree_(&root);
    
    printf("二叉树前序遍历的结果：");
    PreOrderTraversalBinTree(root);

    putchar('\n');
    printf("二叉树中序遍历的结果：");
    InOrderTraversalBinTree(root);
    
    putchar('\n');
    printf("二叉树后序遍历的结果：");
    TailOrderTraversalBinTree(root);
    putchar('\n');
}