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package leetcode;

import java.util.ArrayList;

import java.util.LinkedList;

import java.util.List;

import java.util.Queue;

/**

* Project Name : Leetcode

* Package Name : leetcode

* File Name : BinaryTreeRightSideView

* Creator : Edward

* Date : Aug, 2017

* Description : TODO

*/

public class BinaryTreeRightSideView {

/**

* 199. 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].

root 1 res : 0 level : 1

res : 1, 3, 4

time : O(n);

time ; O(n);

* @param root

* @return

*/

public List<Integer> rightSideView(TreeNode root) {

List<Integer> res = new ArrayList<>();

if (root == null) return res;

helper(res, root, 0);

return res;

}

private void helper(List<Integer> res, TreeNode root, int level) {

if (root == null) return;

if (res.size() == level) {

res.add(root.val);

}

helper(res, root.right, level + 1);

helper(res, root.left, level + 1);

}

public List<Integer> rightSideView2(TreeNode root) {

List<Integer> res = new ArrayList<>();

if (root == null) return res;

Queue<TreeNode> queue = new LinkedList<>();

queue.offer(root);

while (!queue.isEmpty()) {

int size = queue.size();

for (int i = 0; i < size; i++) {

TreeNode cur = queue.poll();

if (i == 0) res.add(cur.val);

if (cur.right != null) queue.offer(cur.right);

if (cur.left != null) queue.offer(cur.left);

}

}

return res;

}

}