leetcode199 - Binary Tree Right Side View - medium

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       <---

 

就是level order traversal, 每层取尾端那个node。同理left view的话就是取每层最头上那个。

 

实现：

class Solution {
public:
    vector<int> rightSideView(TreeNode* root) {
        
        vector<int> res;
        if (!root) return res;
        
        queue<TreeNode*> q;
        q.push(root);
        while (!q.empty()){
            int n = q.size();
            TreeNode* cur;
            while (n){
                cur = q.front();
                q.pop();
                if(cur->left)
                    q.push(cur->left);
                if(cur->right)
                    q.push(cur->right);
                n--;
            }
            res.push_back(cur->val);
        }
        
        return res;
        
    }
};