讀取文件時出現奇怪的錯誤 C++

Question

當我保存playingBoard數組時， save會正確打印它，但是當我嘗試導入使用import創建的save文件時，我會感到奇怪 output - 空格被刪除並替換為1 s，沒有明顯的邏輯。 （示例如下）

最小的可重現示例：

#include <iostream>
#include <fstream>

class Board
{
public:
  char playingBoard[9][9];
  
  Board()
  {
    for (unsigned char i = 0; i < 9; ++i)
      for (unsigned char j = 0; j < 9; ++j)
        playingBoard[i][j] = ' ';
  }

  bool import(std::string filename)
  {
    std::ifstream ifs {filename};
    if (!ifs.is_open())
      return false;

    for (unsigned char i = 0; i < 9; ++i) {
      for (unsigned char j = 0; j < 9; ++j) {
        ifs >> playingBoard[i][j];
        std::cout << playingBoard[i][j] << "|";
      }
      std::cout << std::endl;
    }
  
    ifs.close();
    return true;
  }

  bool save(std::string filename) const
  {
    std::ofstream ofs {filename, std::ios::app};
    if (!ofs.is_open())
      return false;
  
    for (unsigned char i = 0; i < 9; ++i) {
      for (unsigned char j = 0; j < 9; ++j) {
        ofs << playingBoard[i][j];
        std::cout << playingBoard[i][j] << "|";
      }
      std::cout << std::endl;
    }
  
    ofs.close();
    return true;
  }
};

int main()
{
  Board board;
  board.import("filename");
  
  std::cout << std::endl;
  board.playingBoard[1][1] = '1';
  board.save("filename");
}

• output 首次運行（文件之前不存在，因此只有一個輸出）：

   | | | | | | | | | |1| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

• output 在第二次運行：

   1| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 1| | | | | | | | | |1| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

• 第三次運行 output：

   1|1|1| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 1|1|1| | | | | | | |1| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

Answer 1

您的問題是，默認情況下，使用operator >>跳過空格。 您需要使用另一種方法從文件中提取字符，例如get成員 function（下面的示例，使用 gcc-9.3.0 測試）。

  bool import(std::string filename)
  {
    std::ifstream ifs {filename};
    if (!ifs.is_open())
      return false;

    for (unsigned char i = 0; i < 9; ++i) {
      for (unsigned char j = 0; j < 9; ++j) {
        playingBoard[i][j] = ifs.get();
        std::cout << playingBoard[i][j] << "|";
      }
      std::cout << std::endl;
    }

Output：

$ ./a.out 
 | | | | | | | | |
 |1| | | | | | | |
 | | | | | | | | |
 | | | | | | | | |
 | | | | | | | | |
 | | | | | | | | |
 | | | | | | | | |
 | | | | | | | | |
 | | | | | | | | |

 | | | | | | | | |
 |1| | | | | | | |
 | | | | | | | | |
 | | | | | | | | |
 | | | | | | | | |
 | | | | | | | | |
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