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Program.cs
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Program.cs
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using System;
using System.Collections.Generic;
using System.Text;
namespace LetterTilePossibilities
{
class Program
{
static void Main(string[] args)
{
string tiles = "AAB";
Console.WriteLine(NumTilePossibilities(tiles));
}
static int NumTilePossibilities(string tiles)
{
var letters = new int[26];
foreach (var c in tiles)
letters[c - 'A']++;
return DFS(letters);
}
static int DFS(int[] letters)
{
int res = 0;
for (int i = 0; i < letters.Length; i++)
{
if (letters[i] == 0)
continue;
res++;
letters[i]--;
res += DFS(letters);
letters[i]++;
}
return res;
}
}
}