199.binary-tree-right-side-view.go

/*
 * @lc app=leetcode id=199 lang=golang
 *
 * [199] Binary Tree Right Side View
 *
 * https://leetcode.com/problems/binary-tree-right-side-view/description/
 *
 * algorithms
 * Medium (56.29%)
 * Likes:    3534
 * Dislikes: 187
 * Total Accepted:    410.6K
 * Total Submissions: 729.4K
 * Testcase Example:  '[1,2,3,null,5,null,4]'
 *
 * Given the root of 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.
 *
 *
 * Example 1:
 *
 *
 * Input: root = [1,2,3,null,5,null,4]
 * Output: [1,3,4]
 *
 *
 * Example 2:
 *
 *
 * Input: root = [1,null,3]
 * Output: [1,3]
 *
 *
 * Example 3:
 *
 *
 * Input: root = []
 * Output: []
 *
 *
 *
 * Constraints:
 *
 *
 * The number of nodes in the tree is in the range [0, 100].
 * -100 <= Node.val <= 100
 *
 *
 */
package leetgo

// @lc code=start
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func rightSideView(root *TreeNode) []int {
	if root == nil {
		return []int{}
	}

	res := []int{}

	return helper199(root, res, 0)
}

func helper199(node *TreeNode, res []int, depth int) []int {
	if node == nil {
		return res
	}

	if len(res) == depth {
		res = append(res, node.Val)
	}

	res = helper199(node.Right, res, depth+1)
	res = helper199(node.Left, res, depth+1)

	return res
}

// @lc code=end