Binary Tree Right Side View

Description:

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].

Code:

 1    vector<int> rightSideView(TreeNode *root) {

 2         deque<TreeNode*>a;

 3         deque<TreeNode*>b;

 4         vector<int>result;

 5         

 6         if (root==NULL)

 7             return result;

 8             

 9         a.push_back(root);

10         while ( !a.empty() || !b.empty() )

11         {

12             if ( !a.empty() )

13             {

14                 //去队首元素

15                 result.push_back(a.front()->val);

16                 //将a中所有元素的孩子存放到b中,并清空a

17                 while (!a.empty())

18                 {

19                     TreeNode* p = a.front();

20                     if (p->right)

21                         b.push_back(p->right);

22                     if (p->left)

23                         b.push_back(p->left);

24                     a.pop_front();

25                 }

26             }

27             else

28             {

29                 result.push_back(b.front()->val);

30                 //将a中所有元素的孩子存放到b中,并清空a

31                 while (!b.empty())

32                 {

33                     TreeNode* p = b.front();

34                     if (p->right)

35                         a.push_back(p->right);

36                     if (p->left)

37                         a.push_back(p->left);

38                     b.pop_front();

39                 }

40             }

41         }

42          return result;

43     }

View Code