BinaryTreeRightSideView.js

// Source : https://leetcode.com/problems/binary-tree-right-side-view
// Author : Dean Shi
// Date   : 2021-11-09

/***************************************************************************************
 * 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
 * 
 * 
 ***************************************************************************************/

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var rightSideView = function(root) {
    if (!root) return []

    const result = [root.val]

    let currLevel = [root]
    while((currLevel = BFSParse(currLevel)).length > 0) {
        result.push(currLevel[currLevel.length - 1].val)
    }

    return result
};

function BFSParse(queue) {
    const result = []
    for (let item of queue) {
        if (item.left) {
            result.push(item.left)
        }
        if (item.right) {
            result.push(item.right)
        }
    }
    return result
}