Leetcode skimming: binary tree 12 (all paths of binary tree)

257. All paths of binary tree

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Given a binary tree , Return all paths from the root node to the leaf node .

explain : A leaf node is a node that has no children .

Example :

Obviously, the first order traversal of this problem is more comfortable . Use recursion to find the way a little bit .

package com.programmercarl.tree;

import com.programmercarl.util.GenerateTreeNode;

import java.util.ArrayList;
import java.util.List;

/** * @ClassName BinaryTreePaths * @Descriotion TODO * @Author nitaotao * @Date 2022/7/4 18:16 * @Version 1.0 **/
public class BinaryTreePaths {
    
    public static List<String> binaryTreePaths(TreeNode root) {
    
        List<String> result = new ArrayList<String>();
        // The first sequence traversal 
        getPath(root, result, "");
        return result;
    }

    public static void getPath(TreeNode root, List<String> result, String path) {
    
// if (root == null) {
    
// result.add(path.substring(0, path.length() - 2));
// return;
// }
        // The first sequence traversal 
        path += root.val + "->";
        // If there is only one direction left   Route selection 
        if (root.left == null && root.right != null) {
    
            getPath(root.right, result, path);
        } else if (root.left != null && root.right == null) {
    
            getPath(root.left, result, path);
        } else if (root.left == null && root.right == null){
    
            result.add(path.substring(0, path.length() - 2));
            return;
        }else{
    
            getPath(root.left, result, path);
            getPath(root.right, result, path);
        }
    }

    public static void main(String[] args) {
    
        TreeNode node = GenerateTreeNode.generateTreeNode("[1]");
        binaryTreePaths(node);
    }
}