LeetCode102|二叉树的所有路径

示例:

输入:

   1
 /   
2     3
 
  5

输出: ["1->2->5", "1->3"]

解释: 所有根节点到叶子节点的路径为: 1->2->5, 1->3

 

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

public class BinaryTreePathsTest {
    public static void main(String[] args) {
        TreeNode t1 = new TreeNode(1);
        TreeNode t2 = new TreeNode(2);
        TreeNode t3 = new TreeNode(3);
        TreeNode t4 = new TreeNode(5);
        t1.left = t2;
        t1.right = t3;
        t2.right = t4;
        List<String> stringList = binaryTreePaths(t1);
        System.out.println("stringList = " + stringList);

    }

    public static  List<String> binaryTreePaths(TreeNode root) {
        List<String> paths = new ArrayList<>();
        if (root == null) {
            return paths;
        }
        LinkedList<TreeNode> queue = new LinkedList<>();
        LinkedList<String> pathBack = new LinkedList<>();
        queue.add(root);
        pathBack.add(String.valueOf(root.val));

        while (!queue.isEmpty()) {
            TreeNode node = queue.pollLast();
            String path = pathBack.pollLast();
            if (node.left == null && node.right == null) {
                paths.add(path);
            }
            if (node.left != null) {
                queue.add(node.left);
                pathBack.add(path + "->" + node.left.val);
            }
            if (node.right != null) {
                queue.add(node.right);
                pathBack.add(path + "->" + node.right.val);
            }
        }
        return paths;
    }
}