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Question Solution
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.
分析，直观上只需考虑最右边的元素，没有则考虑左儿子，但会出现以下状况
1
/ \
2 3
/
4
我们的解决方案是，以层为单位，使用Queue类，只将每一层最右的节点放入结果list中
public class Solution {
public List<Integer> rightSideView(TreeNode root) {
List<Integer> x=new ArrayList<Integer>();
Queue<TreeNode> queue = new LinkedList<TreeNode>();
if(root!=null)
{
TreeNode z=null;
TreeNode y=null;
queue.add(root);
queue.add(z);
boolean o=false;
while(queue.peek()!=null)
{
o=false;
y=queue.element();
x.add(y.val);
while(y!=null)
{
if(y.right!=null)
{
o=true;
queue.add(y.right);
}
if(y.left!=null)
{
o=true;
queue.add(y.left);
}
queue.remove();
y=queue.element();
}
if(o==true)
queue.add(z);
queue.remove();
}
}
return x;
}
}
Leetcode#199Binary Tree Right Side View
原文：http://7061299.blog.51cto.com/7051299/1649852