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我正在尝试在没有太多 I/O 或使用文本文件经验的情况下完成 CSE 实验室。该程序的目标是根据用户输入的单词和定义创建字典。输出文本文件的格式应该是

条目数(作为数字)

单词

定义

单词

定义

等等。

此时,如果所有单词都是“Alberta”且定义为“Threesome”,则输出显示为:

1

阿尔伯塔

三人行

2艾伯塔省

三人行

2艾伯塔省

三人行

显然有些不对劲。这是生成的代码:如果它很混乱并且输出语句被奇怪地分开,我很抱歉,我已经尝试了一段时间。

#include <iostream>
#include <string>
#include <fstream>
#include <stdlib.h>

using namespace std;
int main() 
{
    string name; // Name of writing/reading document

cout << "Please enter the path (including file name) for the dictionary you want to create: " ;
getline(cin,name); // Inputs name

fstream dicFile;

int addcount = 0; // number of times file has been added to.

int choice = 0; // Controls while loop

while (choice != 3) 
{
    cout << "- - - - - - - - - -" << endl;
    cout << "1) Add a word to the dictionary" << endl;
    cout << "2) Print Dictionary" << endl;
    cout << "3) Quit" << endl;
    cout << "Choose an option from the menu: ";

    string choiceS;
    getline(cin,choiceS);

    choice = atoi(choiceS.c_str());

    string wordAdd; // Stores word to be added
    string defAdd; // Stores definition to be added

    int size = 1; // Number of entries after the first entry

    if(choice > 0 && choice < 4)
    {
        cout << "- - - - - - - - - -" << endl;

        if(choice == 1) 
        {
                            
            if(addcount == 0) 
            {
                dicFile.open(name.c_str(),ios::in|ios::out|ios::app);
                cout << "Enter a word or phrase to add to the dictionary: ";
                getline(cin,wordAdd);
                dicFile << size;
                dicFile << endl;
                dicFile << wordAdd;

                dicFile << endl;

                cout << "Enter the definition for \"" << wordAdd << "\": ";
                getline(cin,defAdd);
                dicFile << defAdd << endl;
    
                dicFile.close();    
                addcount++;
            }
            
            else 
            {
                dicFile.open(name.c_str(),ios::in|ios::out|ios::app);
                size = size + 1;
                dicFile << size;
                dicFile.close();

                dicFile.open(name.c_str(),ios::in|ios::out|ios::app);
                cout << "Enter a word or phrase to add to the dictionary: ";
                getline(cin,wordAdd);
                dicFile << wordAdd;

                dicFile << endl;

                cout << "Enter the definition for \"" << wordAdd << "\": ";
                getline(cin,defAdd);
                dicFile << defAdd << endl;
    
                dicFile.close();
            }

            
        }   

        if(choice == 2)
        {
            if(true)
            {
                dicFile.open(name.c_str(),ios::in);
                
                string readSize;
                int readSizei;
                
                getline(dicFile,readSize);
                readSizei = atoi(readSize.c_str());

                for(int i = 0; i < readSizei*2 + 1; i++)
                {
                    string word;
                    string def;
                    getline(dicFile,word);
                    cout << word << endl;
                    getline(dicFile,def);
                    cout << def << endl;
                }
                dicFile.close();    
            }

            else 
            {   cout << "- - - - - - - - - -" << endl;
                cout << "The dictionary is empty!" << endl;
            }
        }
        
    }

    else 
    {   cout << "- - - - - - - - - -" << endl; 
        cout << "Invalid menu selection (number should be between 1-3)" << endl; 
    }

}
}

为了覆盖文本文件的第一行,但在选择选项 2 时将新定义附加到文件中,我需要做什么?对 I/O 来说相当新。谢谢你的时间。

4

1 回答 1

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您不能“就地”修改现有文件。相反,您必须创建一个新的临时文件,并将所有内容复制到临时文件,并进行所需的修改。然后将临时文件重命名为原始文件,从而替换它。

在伪代码中:

open_old_file();
create_temporary_file();

while (read_line_from_old_file())
{
    do_possible_modifications_to_line();
    write_line_to_temporary_file();
}

close_temporary_file();
close_old_file();

rename_temporary_file_to_old_file();
// or if the above doesn't work:
//   copy_temporary_file_to_old_file();
//   delete_temporary_file();
于 2012-09-30T13:57:57.510 回答