257.Tree.E-binaryTreePaths.js

/**
 * 257
 * Given a binary tree, return all root-to-leaf paths.
 */

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {string[]}
 */
const binaryTreePaths = function(root) {
  if(!root) return [];
  const result = [];
  function path(root, str){
      if(!root.left && !root.right) {
        result.push(str + root.val);
      }
      if(root.left) {
        path(root.left, str + root.val + "->");
      }
      if(root.right) {
        path(root.right, str + root.val + "->");
      }
  }
  path(root, "");
  return result;
};