2024-04-17 07:49:35 +0000 UTC

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func smallestFromLeaf(root *TreeNode) string {
	ans := ""
	var dfs func(node *TreeNode, text string)
	dfs = func(node *TreeNode, text string) {
		if node == nil {
			return
		}
		text = string(rune(node.Val + 97)) + text
		if node.Right == nil && node.Left == nil {
			if ans == "" || ans > text {
				ans = text
			}
			return
		}
		dfs(node.Left, text)
		dfs(node.Right, text)
	}

	dfs(root, "")
	return ans
}