leetcode199二叉树的右视图

给定一棵二叉树，想象自己站在它的右侧，按照从顶部到底部的顺序，返回从右侧所能看到的节点值。

示例:

输入: [1,2,3,null,5,null,4]
输出: [1, 3, 4]
解释:

   1            <---
 /   \
2     3         <---
 \     \
  5     4       <---

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> rightSideView(TreeNode* root) {
        vector<int>  view;
        queue<pair<TreeNode*,int> > Q;
        if(root)
        Q.push(make_pair(root,0));
        while(!Q.empty()){
            int depth = Q.front().second;
            TreeNode *node = Q.front().first;
            Q.pop();
            if(view.size()==depth)
                view.push_back(node->val);
            else
                view[depth]=node->val;
            if(node->left)
                Q.push(make_pair(node->left,depth+1));
            if(node->right)
                Q.push(make_pair(node->right,depth+1));
        }
        return view;
    }
};