加载丑陋的输入 [英] Loading ugly input

问题描述

我需要知道如何在c ++中加载这样的输入

I need to know how to load input like this in c++

{ [1, 1], [2, 10] , [-10, 20] }

在C中我可以这样写：

if ( ( scanf(" %c",&bracket) ) != 1 || bracket != '{') {
    printf("Wrong input.\n");
    return 1;
} // 1st bracket


while(1) {

   if ( ( scanf(" %c%d%c%d%c",&bracket1,&arr[index][0],&dot,&arr[index][1],&bracket2) ) != 5  || bracket1 != '[' || bracket2 != ']' || dot != ',') {
       printf("Wrong input.\n");
       return 1;
   }

   if ( ( scanf(" %c",&tester) ) != 1 || ( tester != ',' && tester != '}' ) ) {
       printf("Wrong input.\n");
       return 1;
   }

   index++;

   if ( tester == '}' ) 
      break;

  } 

但我不知道如何加载它在c ++和修复所有错误的输入。我试图加载它，但它没有工作，不能修复错误的输入与cin。

But i have no idea how to load it in c++ and fix all the wrong inputs. I tried to load it with cin but it did not work and could not fix wrong inputs with cin.

推荐答案

令牌（或词典）中的输入。您输入的是7种类型的令牌： [] {}，number end_of_file 。

You have to break the input in tokens (or lexemes). Your input is made of 7 types of tokens: [ ] { } , number end_of_file.

// tokens definition
enum token
{
  open_obj,
  close_obj,
  open_pair,
  close_pair,
  comma,
  number,
  end
};

// scanner
class scanner_type
{
  std::istream& mis;

public:

  token mt;
  int mn;

  scanner_type( std::istream& ais ) : mis( ais ) {}

  token get()
  {
    std::ws( mis ); // eat white

    char c;
    if ( ! mis.get( c ) )
      return mt = token::end;

    switch ( c )
    {
    case '[': return mt = token::open_pair;
    case ']': return mt = token::close_pair;
    case '{': return mt = token::open_obj;
    case '}': return mt = token::close_obj;
    case ',': return mt = token::comma;
    default:
      if ( std::isdigit( c ) || c == '-' || c == '+' )
      {
        mis.unget();
        mis >> mn;
        return mt = token::number;
      }
      else
      {
        throw "unexpected character";
      }
    };
  }
};

int main()
{
  std::stringstream ss( "{ [1, 1], [2, 10] , [-10, 20] }" );
  scanner_type sc( ss );

  assert( sc.get() == token::open_obj );
  assert( sc.get() == token::open_pair );
  assert( sc.get() == token::number );
  assert( sc.mn == 1 );
  // ...

  return 0;
}

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