#257 Binary Tree Paths

binaryTreePaths.js

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {string[]}
 */
var binaryTreePaths = function(root) {
    
    // 1. traveling the all node with pre order.
    // 2. save the node path.
    // 3. when traveling to the bottom node , pushing the path to result.
    
    let stack = [];
    let current;
    let result =[];
    
    if(!root){
        return [];
    }
    
    stack.push({
        node: root,
        path: root.val + ""
    });
    
    while (stack.length > 0){
        current = stack.pop();
        
        if(current.node.left === null && current.node.right === null){
            result.push(current.path);
        }
            
        if(current.node.right){
            stack.push({
                node: current.node.right,
                path: current.path + "->" + current.node.right.val
            });
        }
        
        if(current.node.left){
             stack.push({
                node: current.node.left,
                path: current.path + "->" + current.node.left.val
            });
        }
    }
    return result;
};