[leetcode] Binary Tree Right Side View

Binary Tree Right Side View

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.

For example:
Given the following binary tree,

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

You should return [1, 3, 4].

Credits:
Special thanks to @amrsaqr for adding this problem and creating all test cases.

 

思路：层次遍历，取每层最后一个节点。

 

/**
* 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> ret;
    queue<TreeNode*> myque;

    if(NULL == root) return ret;
    myque.push(root);
    int len = 0;
    TreeNode *ptr;

    while(!myque.empty())
    {
      len = myque.size();
      for(int i=0; i<len; i++)
      {
        ptr = myque.front();
        myque.pop();

        if(ptr->left) myque.push(ptr->left);
        if(ptr->right) myque.push(ptr->right);
      }
      ret.push_back(ptr->val);
    }

    return ret;
  }
};