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  1. using System;
  2.  
  3. class Program
  4. {
  5.   static void Main(string[] args)
  6.   {
  7.     string[] data = new string[] {
  8.       "a",
  9.       "1",
  10.       "0",
  11.       "+0",
  12.       "-0",
  13.       "01",
  14.       "+12345",
  15.       "-12345",
  16.       "1.2",
  17.       "1.2.3",
  18.       "12-3",
  19.       "1a",
  20.       "+1",
  21.       "-0.123",
  22.       "1.2e2",
  23.       "1.2E2",
  24.       "1.2e",
  25.       "1.2e+3",
  26.       "1.2e-3",
  27.       "1.2e-3.5",
  28.       ".5",
  29.       ".5e2",
  30.       "5.e2",
  31.     };
  32.  
  33.     Checker ic = new IntChecker();
  34.     foreach (string str in data)
  35.     {
  36.       ic.Reset();
  37.       Console.Write(str + " : ");
  38.       foreach (char ch in str)
  39.       {
  40.         if (ic.IsError())
  41.         {
  42.           break;
  43.         }
  44.  
  45.         ic.Next(ch);
  46.       }
  47.  
  48.       if (ic.IsAcceptable())
  49.       {
  50.         Console.WriteLine("int({0})", int.Parse(str));
  51.       }
  52.       else
  53.       {
  54.         Console.WriteLine("NaN({0})", str);
  55.       }
  56.     }
  57.   }
  58. }
  59.  
  60. interface Checker
  61. {
  62.   void Reset();
  63.   void Next(char ch);
  64.   bool IsAcceptable();
  65.   bool IsError();
  66. }
  67.  
  68. class IntChecker : Checker
  69. {
  70.   enum IntParsingState
  71.   {
  72.     Error,
  73.     State0,
  74.     State1,
  75.     State2,
  76.     State3,
  77.   }
  78.  
  79.   IntParsingState _state;
  80.  
  81.   public IntChecker()
  82.   {
  83.     Reset();
  84.   }
  85.  
  86.   public void Reset()
  87.   {
  88.     _state = IntParsingState.State0;
  89.   }
  90.  
  91.   public void Next(char ch)
  92.   {
  93.     switch (_state)
  94.     {
  95.       case IntParsingState.State0:
  96.         if (ch == '-' ||
  97.           ch == '+')
  98.         {
  99.           _state = IntParsingState.State1;
  100.         }
  101.         else if (ch == '1' ||
  102.           ch == '2' ||
  103.           ch == '3' ||
  104.           ch == '4' ||
  105.           ch == '5' ||
  106.           ch == '6' ||
  107.           ch == '7' ||
  108.           ch == '8' ||
  109.           ch == '9')
  110.         {
  111.           _state = IntParsingState.State2;
  112.         }
  113.         else if (ch == '0')
  114.         {
  115.           _state = IntParsingState.State3;
  116.         }
  117.         else
  118.         {
  119.           _state = IntParsingState.Error;
  120.         }
  121.         break;
  122.       case IntParsingState.State1:
  123.         if (ch == '1' ||
  124.           ch == '2' ||
  125.           ch == '3' ||
  126.           ch == '4' ||
  127.           ch == '5' ||
  128.           ch == '6' ||
  129.           ch == '7' ||
  130.           ch == '8' ||
  131.           ch == '9')
  132.         {
  133.           _state = IntParsingState.State2;
  134.         }
  135.         else if (ch == '0')
  136.         {
  137.           _state = IntParsingState.State3;
  138.         }
  139.         else
  140.         {
  141.           _state = IntParsingState.Error;
  142.         }
  143.         break;
  144.       case IntParsingState.State2:
  145.         if (ch == '0' ||
  146.           ch == '1' ||
  147.           ch == '2' ||
  148.           ch == '3' ||
  149.           ch == '4' ||
  150.           ch == '5' ||
  151.           ch == '6' ||
  152.           ch == '7' ||
  153.           ch == '8' ||
  154.           ch == '9')
  155.         {
  156.           _state = IntParsingState.State2;
  157.         }
  158.         else
  159.         {
  160.           _state = IntParsingState.Error;
  161.         }
  162.         break;
  163.       case IntParsingState.State3:
  164.       case IntParsingState.Error:
  165.         _state = IntParsingState.Error;
  166.         break;
  167.     }
  168.   }
  169.  
  170.   public bool IsAcceptable()
  171.   {
  172.     return
  173.       _state == IntParsingState.State2 ||
  174.       _state == IntParsingState.State3;
  175.   }
  176.  
  177.   public bool IsError()
  178.   {
  179.     return _state == IntParsingState.Error;
  180.   }
  181. }
  182.  
Success #stdin #stdout 0.02s 131520KB
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stdin
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Standard input is empty
stdout
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a : NaN(a)
1 : int(1)
0 : int(0)
+0 : int(0)
-0 : int(0)
01 : NaN(01)
+12345 : int(12345)
-12345 : int(-12345)
1.2 : NaN(1.2)
1.2.3 : NaN(1.2.3)
12-3 : NaN(12-3)
1a : NaN(1a)
+1 : int(1)
-0.123 : NaN(-0.123)
1.2e2 : NaN(1.2e2)
1.2E2 : NaN(1.2E2)
1.2e : NaN(1.2e)
1.2e+3 : NaN(1.2e+3)
1.2e-3 : NaN(1.2e-3)
1.2e-3.5 : NaN(1.2e-3.5)
.5 : NaN(.5)
.5e2 : NaN(.5e2)
5.e2 : NaN(5.e2)
https://ideone.com/P1j7aZ
language:
C# (gmcs 5.20.1)
created:
5 years ago
visibility:
secret

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