题目：

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代码（首刷看解析）：

class Solution {
public:vector<int> rightSideView(TreeNode* root) {unordered_map<int,int> rightmostvalue;queue<TreeNode*> nodeQueue;queue<int> depthQueue;int maxDepth=-1;nodeQueue.push(root);depthQueue.push(0);while(!nodeQueue.empty()){TreeNode* node = nodeQueue.front();nodeQueue.pop();int depth = depthQueue.front();depthQueue.pop();if(node!=nullptr){maxDepth = max(maxDepth,depth);//下面这一行运用了unordered_map的特性更新，直到最右值rightmostvalue[depth]=node->val;nodeQueue.push(node->left);nodeQueue.push(node->right);depthQueue.push(depth+1);depthQueue.push(depth+1);}}vector<int> ans;for(int i=0;i<=maxDepth;++i){ans.push_back(rightmostvalue[i]);}return ans;}
};