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  1. import java.util.*;
  2. import java.io.*;
  3. public class Main
  4. {
  5.   static ArrayList<String> arr = new ArrayList<>();
  6.   static void gen()
  7.   {
  8.     for(int i = 0; i<26; i++)
  9.     {
  10.       arr.add(nextChar(i)+"");
  11.     }
  12.  
  13.     for(int i = 0; i<26; i++)
  14.     {
  15.       for(int j = 0; j<26; j++)
  16.       {
  17.         arr.add(nextChar(i)+""+nextChar(j));
  18.       }
  19.     }
  20.  
  21.     for(int i = 0; i<26; i++)
  22.     {
  23.       for(int j = 0; j<26; j++)
  24.       {
  25.         for(int k = 0; k<26; k++)
  26.         {
  27.           arr.add(nextChar(i)+""+nextChar(j)+""+nextChar(k));
  28.         }
  29.       }
  30.     }
  31.  
  32. //    Collections.sort(arr);
  33.   }
  34.  
  35.   static char nextChar(int n)
  36.   {
  37.     return (char)(n+'a');
  38.   }
  39.  
  40.   public static void main(String[] args) throws IOException
  41.   {
  42. //    Scanner read = new Scanner(System.in);
  43.     Reader read = new Reader();
  44.  
  45.     gen();
  46. //    for(int i = 0; i<100; i++)
  47. //    {
  48. //      System.out.println(arr.get(i));
  49. //    }
  50.     int tc = read.nextInt();
  51.     for(int cs = 1; cs<=tc; cs++)
  52.     {
  53.       int n = read.nextInt();
  54.       String s = read.readLine();
  55.  
  56.       for(int i = 0; i<arr.size(); i++)
  57.       {
  58.         if(!s.contains(arr.get(i)))
  59.         {
  60.           System.out.println(arr.get(i));
  61.           break;
  62.         }
  63.       }
  64.     }
  65.   }
  66. }
  67.  
  68. class Reader
  69. {
  70.   final private int BUFFER_SIZE = 1 << 16;
  71.   private DataInputStream din;
  72.   private byte[] buffer;
  73.   private int bufferPointer, bytesRead;
  74.  
  75.   public Reader()
  76.   {
  77.     din = new DataInputStream(System.in);
  78.     buffer = new byte[BUFFER_SIZE];
  79.     bufferPointer = bytesRead = 0;
  80.   }
  81.  
  82.   public Reader(String file_name) throws IOException
  83.   {
  84.     din = new DataInputStream(new FileInputStream(file_name));
  85.     buffer = new byte[BUFFER_SIZE];
  86.     bufferPointer = bytesRead = 0;
  87.   }
  88.  
  89.   public String readLine() throws IOException
  90.   {
  91.     byte[] buf = new byte[10000]; // line length
  92.     int cnt = 0, c;
  93.     while ((c = read()) != -1)
  94.     {
  95.       if (c == '\n')
  96.         break;
  97.       buf[cnt++] = (byte) c;
  98.     }
  99.     return new String(buf, 0, cnt);
  100.   }
  101.  
  102.   public int nextInt() throws IOException
  103.   {
  104.     int ret = 0;
  105.     byte c = read();
  106.     while (c <= ' ')
  107.       c = read();
  108.     boolean neg = (c == '-');
  109.     if (neg)
  110.       c = read();
  111.     do
  112.     {
  113.       ret = ret * 10 + c - '0';
  114.     }  while ((c = read()) >= '0' && c <= '9');
  115.  
  116.     if (neg)
  117.       return -ret;
  118.     return ret;
  119.   }
  120.  
  121.   public long nextLong() throws IOException
  122.   {
  123.     long ret = 0;
  124.     byte c = read();
  125.     while (c <= ' ')
  126.       c = read();
  127.     boolean neg = (c == '-');
  128.     if (neg)
  129.       c = read();
  130.     do {
  131.       ret = ret * 10 + c - '0';
  132.     }
  133.     while ((c = read()) >= '0' && c <= '9');
  134.     if (neg)
  135.       return -ret;
  136.     return ret;
  137.   }
  138.  
  139.   public double nextDouble() throws IOException
  140.   {
  141.     double ret = 0, div = 1;
  142.     byte c = read();
  143.     while (c <= ' ')
  144.       c = read();
  145.     boolean neg = (c == '-');
  146.     if (neg)
  147.       c = read();
  148.  
  149.     do {
  150.       ret = ret * 10 + c - '0';
  151.     }
  152.     while ((c = read()) >= '0' && c <= '9');
  153.  
  154.     if (c == '.')
  155.     {
  156.       while ((c = read()) >= '0' && c <= '9')
  157.       {
  158.         ret += (c - '0') / (div *= 10);
  159.       }
  160.     }
  161.  
  162.     if (neg)
  163.       return -ret;
  164.     return ret;
  165.   }
  166.  
  167.   private void fillBuffer() throws IOException
  168.   {
  169.     bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
  170.     if (bytesRead == -1)
  171.       buffer[0] = -1;
  172.   }
  173.  
  174.   private byte read() throws IOException
  175.   {
  176.     if (bufferPointer == bytesRead)
  177.       fillBuffer();
  178.     return buffer[bufferPointer++];
  179.   }
  180.  
  181.   public void close() throws IOException
  182.   {
  183.     if (din == null)
  184.       return;
  185.     din.close();
  186.   }
  187. }
Success #stdin #stdout 0.18s 57604KB
comments (?)
stdin
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3
28
qaabzwsxedcrfvtgbyhnujmiklop
13
cleanairactbd
10
aannttoonn
stdout
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ac
f
b
https://ideone.com/UZYIEW
language:
Java (HotSpot 12)
created:
2 years ago
visibility:
public

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