Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.
Example:
Input: [1,2,3,null,5,null,4] Output: [1, 3, 4] Explanation: 1 <--- / \ 2 3 <--- \ \ 5 4 <---
思路：
我们利用分层遍历的思想，将每一层的最后一个数放到结果中，这里请注意对如何更新最后一个数的处理：
class Solution {
public:
vector<int> rightSideView(TreeNode* root) {
queue<TreeNode*> d;
vector<int> res;
TreeNode *last = root;
d.push(root);
while (root) {
if (root->left) d.push(root->left);
if (root->right) d.push(root->right);
if (root == last) { res.push_back(root->val); last = d.back(); }
d.pop();
if(!d.empty()) root = d.front();
else root = NULL;
}
return res;
}
};