/**
 * 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 {string[]}
 */
var binaryTreePaths = function(root) {
    if (!root) return root;
    const result = [];
    
    const dfsPath = (root, str = "") => {
        if (!root) return;
        // leaf reached
        if (!root.left && !root.right) {
            result.push(str + root.val)
        }
        
        dfsPath(root.left, str + root.val + "->");
        dfsPath(root.right, str + root.val + "->");
    }
    
    // start dfs
    dfsPath(root);
    
    return result;
};