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Program.cs
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Program.cs
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//回溯算法,用DFS拼串,每次更新maxLen。
//注意需要额外检查一下,每个字符串本身是否有重复字母。
using System;
using System.Collections.Generic;
namespace MaximumLength
{
class Program
{
static void Main(string[] args)
{
string[] arr = { "yy","bkhwmpbiisbldzknpm" };
Console.WriteLine(MaxLength(arr));
}
static int maxLen;
static int MaxLength(IList<string> arr)
{
var letters = new HashSet<char>();
var cur = "";
Generate(arr, cur, -1, letters);
return maxLen;
}
static void Generate(IList<string> arr, string cur, int index, HashSet<char> letters)
{
maxLen = Math.Max(maxLen, cur.Length);
for (int i = index + 1; i < arr.Count; i++)
{
bool unique = true;
var selfCheck = new HashSet<char>();
foreach (var letter in arr[i])
{
if (letters.Contains(letter) || !selfCheck.Add(letter))
{
unique = false;
break;
}
}
if (unique)
{
foreach (var letter in arr[i])
letters.Add(letter);
Generate(arr, cur + arr[i], i, letters);
foreach (var letter in arr[i])
letters.Remove(letter);
}
}
}
}
}