257. Binary Tree Paths

题目

Given a binary tree, return all root-to-leaf paths.

Note: A leaf is a node with no children.

Example:

Input:

   1
 /   \
2     3
 \
  5

Output: ["1->2->5", "1->3"]

Explanation: All root-to-leaf paths are: 1->2->5, 1->3

题目大意

给定一个二叉树，返回所有从根节点到叶子节点的路径。说明: 叶子节点是指没有子节点的节点。

解题思路

• Google 的面试题，考察递归

代码

package leetcode

import (
	"strconv"
)

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func binaryTreePaths(root *TreeNode) []string {
	if root == nil {
		return []string{}
	}
	res := []string{}
	if root.Left == nil && root.Right == nil {
		return []string{strconv.Itoa(root.Val)}
	}
	tmpLeft := binaryTreePaths(root.Left)
	for i := 0; i < len(tmpLeft); i++ {
		res = append(res, strconv.Itoa(root.Val)+"->"+tmpLeft[i])
	}
	tmpRight := binaryTreePaths(root.Right)
	for i := 0; i < len(tmpRight); i++ {
		res = append(res, strconv.Itoa(root.Val)+"->"+tmpRight[i])
	}
	return res
}

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