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Program.cs
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Program.cs
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using System;
using System.Collections.Generic;
namespace SmallestStringStartingFromLeaf
{
public class TreeNode
{
public int val;
public TreeNode left;
public TreeNode right;
public TreeNode(int val = 0, TreeNode left = null, TreeNode right = null)
{
this.val = val;
this.left = left;
this.right = right;
}
}
class Program
{
static void Main(string[] args)
{
var a = new TreeNode(25);
var b = new TreeNode(1);
var c = new TreeNode(3);
var d = new TreeNode(1);
var e = new TreeNode(3);
var f = new TreeNode(0);
var g = new TreeNode(2);
a.left = b;
a.right = c;
b.left = d;
b.right = e;
c.left = f;
c.right = g;
Console.WriteLine(SmallestFromLeaf(a));
}
static string SmallestFromLeaf(TreeNode root)
{
var res = "";
DFS(root, new List<char>(), ref res);
return res;
}
static void DFS(TreeNode node, List<char> path, ref string res)
{
if(node == null) return;
path.Add((char)(node.val + 'a'));
if (node.left == node.right)
{
var temp = new List<char>(path);
temp.Reverse();
var word = string.Join("", temp);
if (res == "" || word.CompareTo(res) < 0)
res = word;
}
DFS(node.left, path, ref res);
DFS(node.right, path, ref res);
path.RemoveAt(path.Count - 1);
}
}
}