199. Binary Tree Right Side View

[Tcdian]

199. Binary Tree Right Side View

给定一棵二叉树，想象自己站在它的右侧，按照从顶部到底部的顺序，返回从右侧所能看到的节点值。

Example

Input: [1,2,3,null,5,null,4]
Output: [1, 3, 4]
Explanation:

   1            <---
 /   \
2     3         <---
 \     \
  5     4       <---

[Tcdian]

Solution ( BFS )

• JavaScript Solution

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

    const queue = [[root, 0]];
    const result = [];

    while (queue.length !== 0) {
        const [node, depth] = queue.shift();
        result[depth] = node.val;
        if (node.left) {
            queue.push([node.left, depth + 1]);
        }
        if (node.right) {
            queue.push([node.right, depth + 1]);
        }
    }
    
    return result;
};