package com.leecode.tree;

import java.util.ArrayList;

import java.util.List;

public class code03hasPathStr {

public List<String> binaryTreePaths(treeNode root) {

//在外部创建list存储所有路径

List<String>res = new ArrayList<>();

helper(root,"",res);

return res;

}

public void helper(treeNode root, String temp, List<String>res){

if (root!=null){

// temp += root.val + ""; 这种方法耗费时间

//将该节点的值并入字符串，再做判断是否可以返回，保证结束时不会多加一个 ->

temp += Integer.toString(root.val);

if((root.left==null) && (root.right==null)){

res.add(temp);}

else {

//不是叶子进行箭头链接

temp+="->";

helper(root.left, temp, res);//temp进入后，再出来进入右枝

helper(root.right, temp, res);

}

}

}

public static void main(String[] args) {

treeNode root1 = new treeNode(1);

treeNode node2 = new treeNode(2);

treeNode node3 = new treeNode(3);

treeNode node4 = new treeNode(4);

root1.left=node2;

root1.right=node3;

node3.right=node4;

code03hasPathStr method=new code03hasPathStr();

List<String> res=method.binaryTreePaths(root1);

System.out.println(res);

}

}