C++二叉树的建立以及遍历

最近在刷 leetcode 的题目，初学算法，菜鸟一枚，写博客记录下常用代码，以备以后查阅，如果代码出现问题，请各位高手指教

void CreatBiTree(TreeNode* &T) {
char ch;

if ((ch = getchar()) == '#')
T = NULL;
else {
T = new TreeNode;
T->val = ch;
CreatBiTree(T->left);
CreatBiTree(T->right);
}
}
void PreOrderTraverse(TreeNode* &T) { // 先序遍历二叉树
if (T!=NULL) { // 当节点不为空时执行
cout << T->val;
PreOrderTraverse(T->left);
PreOrderTraverse(T->right);
}
else
cout << "";
}
int main()
{
Solution s;
TreeNode *head=new TreeNode;

int a[7] = {1,2,2,3,4,4,3};
int flag;
CreatBiTree(head);
cout << "创建完成" << endl;
PreOrderTraverse(head);
cout << "前序遍历" << endl;

system("pause");

}