/**

* Definition for a binary tree node.

* public class TreeNode {

* int val;

* TreeNode left;

* TreeNode right;

* TreeNode(int x) { val = x; }

* }

*/

public class BinaryTreeRightSideView {

//Iterative solution

public List<Integer> rightSideView0(TreeNode root) {

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

if (root == null) {

return result;

}

Deque<TreeNode> queue = new ArrayDeque<>();

queue.offer(root);

while(!queue.isEmpty()) {

TreeNode node = null;

int size = queue.size();

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

node = queue.poll();

if (node.left != null) {

queue.offer(node.left);

}

if (node.right != null) {

queue.offer(node.right);

}

}

result.add(node.val);

}

return result;

}

// Recursive solution

private static void rightSideViewRecursive(TreeNode root, int level, List<Integer> result) {

if (root != null) {

if (level >= result.size()) {

result.add(root.val);

}

rightSideViewRecursive(root.right, level+1, result);

rightSideViewRecursive(root.left, level+1, result);

}

}

public List<Integer> rightSideView(TreeNode root) {

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

rightSideViewRecursive(root, 0, result);

return result;

}

}