binary-tree-level-order-traversal.go

package Problem0102

import (
	"github.com/aQuaYi/LeetCode-in-Golang/kit"
)

type TreeNode = kit.TreeNode

func levelOrder(root *TreeNode) [][]int {
	res := [][]int{}
	var dfs func(*TreeNode, int)

	dfs = func(root *TreeNode, level int) {
		if root == nil {
			return
		}

		// 出现了新的 level
		if  level >= len(res)   {
			res = append(res, []int{})
		}
		res[level] = append(res[level], root.Val)

		dfs(root.Left, level+1)
		dfs(root.Right, level+1)
	}

	dfs(root, 0)

	return res
}