1.打印二叉树
程序很简单，但是其中犯了一个小错误，死活找不到，写代码要注意啊
这里左右子树，要注意是node->left，结果写成root->left
vector<int> PrintFromTopToBottom(TreeNode *root) { vector<int> res; if (NULL == root) return res; TreeNode* node; deque<TreeNode*> tmp; tmp.push_back(root); while (tmp.size()) { node = tmp.front(); res.push_back(node->val); tmp.pop_front(); if (node->left) tmp.push_back(node->left); if (node->right) tmp.push_back(node->right); } return res; }