107. 二叉树的层序遍历 II

二叉树的层序遍历 II

• 难度: medium
• 原始链接: https://leetcode.cn/problems/binary-tree-level-order-traversal-ii
• 标签: 深度优先遍历

解法一: 深度优先遍历

go

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func levelOrderBottom(root *TreeNode) [][]int {
  var ans [][]int
  var dfs func(node *TreeNode, depth int)
  dfs = func(node *TreeNode, depth int) {
    if node == nil {
      return
    }
    if len(ans) <= depth {
      ans = append(ans, []int{})
    }
    ans[depth] = append(ans[depth], node.Val)
    dfs(node.Left, depth+1)
    dfs(node.Right, depth+1)
  }
  dfs(root, 0)
  slices.Reverse(ans)
  return ans
}