Algorithms—257.Binary Tree Paths

思路：找到所有的路径，然后读数。

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public List<String> binaryTreePaths(TreeNode root) {    List<String> ansList=new ArrayList<String>();        if (root!=null) {List<List<TreeNode>> totalList=new ArrayList<List<TreeNode>>();List<TreeNode> initList=new ArrayList<TreeNode>();initList.add(root);totalList.add(initList);for (int i = 0; i < totalList.size(); i++) {List<TreeNode> list=totalList.get(i);TreeNode node=list.get(list.size()-1);boolean flag=false;if (node.left!=null) {List<TreeNode> leftList=new ArrayList<TreeNode>();leftList.addAll(list);leftList.add(node.left);totalList.add(leftList);flag=true;}if (node.right!=null) {List<TreeNode> rightList=new ArrayList<TreeNode>();rightList.addAll(list);rightList.add(node.right);totalList.add(rightList);flag=true;}if (flag) {totalList.remove(i);i--;}}for (int i = 0; i < totalList.size(); i++) {List<TreeNode> list=totalList.get(i);String ans=""+list.get(0).val;for (int j = 1; j < list.size(); j++) {ans+=("->"+list.get(j).val);}ansList.add(ans);}}    return ansList;    }}

耗时：312ms。