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Formatierte Eingabe

Die folgende Lösung kann mehr als die Aufgabenstellung fordert. Sie bietet nicht nur Methoden Read, ReadInt und ReadFloat, sondern auch Methoden zum Lesen von W├Ârtern, Strings, Zeilen usw.

Eine detaillierte Dokumentation dieser Klasse findet man hier.

/In/In.cs
/*-------------------------------------------------------------------------
In.cs -- Formatted Input in C#,
Copyright (c) 2005 Hanspeter Moessenboeck, University of Linz

This class is free software; you can redistribute it and/or modify it 
under the terms of the GNU General Public License as published by the 
Free Software Foundation; either version 2, or (at your option) any 
later version.

This class is distributed in the hope that it will be useful, but 
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License 
for more details.
-------------------------------------------------------------------------*/
using System;
using System.IO;
using System.Text;
using System.Collections;
using System.Globalization;

public class In {
  public  const char eof   = '\uffff';   // signals end of file
  private const char empty = '\ufffe';   // signals: no lookahead character available
  
  private static bool done = true;       // success of most recent operation
  private static StreamReader r = null;  // input stream
  private static char ch = ' ';          // auxiliary for reading
  private static char buf = empty;       // the lookahead character
  private static NumberFormatInfo provider = null; // for conversions between string and float
  private static Stack readerStack = new Stack();  // for nested calls of Open()
  private static Stack bufStack = new Stack();     // for nested calls of Open()
  
  
  public static bool Done {
    get {return done;}
  }
  
  public static void Open(string path) {
    try {
      Open(new FileStream(path, FileMode.Open));
    } catch {
      done = false;
    }
  }
  
  public static void Open(Stream s) {
    StreamReader rNew = new StreamReader(s);
    readerStack.Push(r);
    bufStack.Push(buf);
    r = rNew;
    buf = empty;
    done = true;
  }
  
  public static void Close() {
    if (r != null) r.Close();
    if (readerStack.Count > 0) {
      r = (StreamReader)readerStack.Pop();
      buf = (char)bufStack.Pop();
    } else {
      r = null;
      buf = empty;
    }
  }
  
  private static char CharAfterWhiteSpace() {
    char ch;
    do ch = Read(); while (ch <= ' ');
    return ch;
  }
  
  private static string ReadDigits() {
    StringBuilder b = new StringBuilder();
    char ch = CharAfterWhiteSpace();
    if (ch == '-') {
      b.Append(ch);
      ch = Read();
    }
    while (Char.IsDigit(ch)) {
      b.Append(ch);
      ch = Read();
    }
    buf = ch;
    return b.ToString();
  }
  
  private static string ReadFloatDigits() {
    StringBuilder b = new StringBuilder();
    char ch = CharAfterWhiteSpace();
    if (ch == '+' || ch == '-') {
      b.Append(ch);
      ch = Read();
    }
    while (Char.IsDigit(ch)) {
      b.Append(ch);
      ch = Read();
    }
    if (ch == '.') {
      b.Append(ch);
      ch = Read();
      while (Char.IsDigit(ch)) {
        b.Append(ch);
        ch = Read();
      }
    }
    if (ch == 'e' || ch == 'E') {
      b.Append(ch);
      ch = Read();
      if (ch == '+' || ch == '-') {
        b.Append(ch);
        ch = Read();
      }
      while (Char.IsDigit(ch)) {
        b.Append(ch);
        ch = Read();
      }
    }
    buf = ch;
    return b.ToString();
  }

  public static char Read() {
    if (buf != empty) {
      ch = buf;
      if (buf != eof) buf = empty;
    } else {
      int x;
      if (r == null) x = Console.Read(); else x = r.Read();
      if (x < 0) {
        ch = eof; buf = eof; done = false;
      } else {
        ch = (char)x;
      }
    }
    return ch;
  }
  
  public static int ReadInt() {
    string s = ReadDigits();
    try {
      done = true;
      return Convert.ToInt32(s);
    } catch {
      done = false;
      return 0;
    }
  }
  
  public static long ReadLong() {
    string s = ReadDigits();
    try {
      done = true;
      return Convert.ToInt64(s);
    } catch {
      done = false;
      return 0;
    }
  }
  
  public static float ReadFloat() {
    string s = ReadFloatDigits();
    try {
      done = true;
      return Convert.ToSingle(s, provider);
    } catch {
      done = false;
      return 0f;
    }
  }
  
  public static double ReadDouble() {
    string s = ReadFloatDigits();
    try {
      done = true;
      return Convert.ToDouble(s, provider);
    } catch {
      done = false;
      return 0.0;
    }
  }
  
  public static bool ReadBool() {
    string s = ReadIdent();
    done = true;
    if (s == "true") return true;
    else if (s == "false") return false;
    else {done = false; return false;}
  }
  
  public static string ReadIdent() {
    StringBuilder b = new StringBuilder();
    char ch = CharAfterWhiteSpace();
    if (Char.IsLetter(ch) || ch == '_') {
      b.Append(ch);
      ch = Read();
      while (Char.IsLetterOrDigit(ch) || ch == '_') {
        b.Append(ch);
        ch = Read();
      }
    }
    buf = ch;
    done = b.Length > 0;
    return b.ToString();
  }
  
  public static string ReadString() {
    StringBuilder b = new StringBuilder();
    char ch = CharAfterWhiteSpace();
    if (ch == '"') {
      ch = Read();
      while (ch != eof && ch != '"') {
        b.Append(ch);
        ch = In.Read();
      }
      if (ch == '"') {done = true; ch = Read();} else done = false;
    } else done = false;
    buf = ch;
    return b.ToString();
  }
  
  public static string ReadWord() {
    StringBuilder b = new StringBuilder();
    char ch = CharAfterWhiteSpace();
    while (ch > ' ' && ch != eof) {
      b.Append(ch);
      ch = Read();
    }
    buf = ch;
    done = b.Length > 0;
    return b.ToString();
  }
  
  public static string ReadLine() {
    StringBuilder b = new StringBuilder();
    char ch = Read();
    done = ch != eof;
    while (ch != eof && ch != '\r') {
      b.Append(ch);
      ch = Read();
    }
    Read(); // skip '\n'
    buf = empty;
    return b.ToString();
  }
  
  public static string ReadFile() {
    StringBuilder b = new StringBuilder();
    char ch = Read();
    while (done) {
      b.Append(ch);
      ch = Read();
    }
    buf = eof;
    done = true;
    return b.ToString();
  }

  public static char Peek() {
    char ch = CharAfterWhiteSpace();
    buf = ch;
    return ch;
  }
  
  static In() {
    provider = new CultureInfo("en-US").NumberFormat;
  }
  
}