【leetcode刷题】T128-二叉树的右视图

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.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def rightSideView(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """
        if not root:
            return []
        res = [0]
        p = [root]
        q = []
        while len(p) != 0 or len(q) != 0:
            if len(p) == 0:
                p = q
                q = []
                res.append(0)
            tmp = p.pop(0)
            res[-1] = tmp.val
            if tmp.left:
                q.append(tmp.left)
            if tmp.right:
                q.append(tmp.right)
        return res

/**
 * 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> res;
        if(!root)
            return res;
        res.push_back(0);
        queue<TreeNode*> p;
        queue<TreeNode*> q;
        p.push(root);
        while(p.size() != 0 || q.size() != 0){
            if(p.size() == 0){
                while(q.size() != 0){
                    p.push(q.front());
                    q.pop();
                }
                res.push_back(0);
            }
            TreeNode* tmp = p.front();
            p.pop();
            res[res.size()-1] = tmp->val;
            if(tmp->left)
                q.push(tmp->left);
            if(tmp->right)
                q.push(tmp->right);
        }
        return res;
    }
};