题目：

题解：

class Solution {
public:vector<int> rightSideView(TreeNode* root) {unordered_map<int, int> rightmostValueAtDepth;int max_depth = -1;stack<TreeNode*> nodeStack;stack<int> depthStack;nodeStack.push(root);depthStack.push(0);while (!nodeStack.empty()) {TreeNode* node = nodeStack.top();nodeStack.pop();int depth = depthStack.top();depthStack.pop();if (node != NULL) {// 维护二叉树的最大深度max_depth = max(max_depth, depth);// 如果不存在对应深度的节点我们才插入if (rightmostValueAtDepth.find(depth) == rightmostValueAtDepth.end()) {rightmostValueAtDepth[depth] =  node -> val;}nodeStack.push(node -> left);nodeStack.push(node -> right);depthStack.push(depth + 1);depthStack.push(depth + 1);}}vector<int> rightView;for (int depth = 0; depth <= max_depth; ++depth) {rightView.push_back(rightmostValueAtDepth[depth]);}return rightView;}
};