AI solution for JavaScript Coding Question on BFE.dev
137. binary tree vertical traversal

One possible solution to this problem is to use a hash table to store the nodes by their horizontal positions, and a priority queue to sort the nodes within each horizontal position based on their vertical positions inherited from their parent nodes.

Here's the JavaScript code:

/**

• 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 verticalTraversal = function(root) { const hash = new Map(); const queue = [[root, 0, 0]];

while (queue.length > 0) {
    const [node, x, y] = queue.shift();
    if (!hash.has(x)) {
        hash.set(x, []);
    }
    const nodes = hash.get(x);
    nodes.push([node.val, y]);
    if (node.left) {
        queue.push([node.left, x - 1, y + 1]);
    }
    if (node.right) {
        queue.push([node.right, x + 1, y + 1]);
    }
}

const keys = Array.from(hash.keys()).sort((a, b) => a - b);
const result = [];
for (const key of keys) {
    const nodes = hash.get(key);
    nodes.sort((a, b) => {
        if (a[1] !== b[1]) {
            return a[1] - b[1];
        } else {
            return a[0] - b[0];
        }
    });
    nodes.forEach(n => result.push(n[0]));
}

return result;

};