为什么解析我读取的行的内部循环通过外部读取循环每隔一次迭代都被跳过？

Question

#include <iostream>  
#include <iomanip>
#include <string>
#include <fstream>
#include <cmath>
#include <cstdlib>
#include <sstream>

using namespace std;

int main(int argc, char* argv[])
{;
    int arraylen = 7, arraylen_new = 0, i = 0, nextstep = 0;
    string line, field, junkText;
    string* randNum = new string[arraylen];
    string* phrase = new string[arraylen];

    ifstream randomTxt;
    arraylen = 5;

    randomTxt.open("random.txt");

    while(!randomTxt.eof())
    {
        getline(randomTxt,line);
        stringstream ss(line);
        nextstep = 0;
        while(getline(ss,field,','))
        {
            cout << i << endl;
            /*if(nextstep == 0)
            {
                randNum[i] = field;
                cout<< "number " << i << ": " << randNum[i] << endl;
                nextstep = 1;
            }

            else if(nextstep == 1)
            {
                junkText = field;
                cout<< "junk " << i << ": " << junkText << endl;
                nextstep = 2;               
            }
            else
            {
                items[i] = field;
                cout<< "items " << i << ": " << items[i] << endl;
            }*/

            if(i == (arraylen-1))
            {
                arraylen_new = arraylen + 1;
                string* temp1 = new string[arraylen_new];
                string* temp2 = new string[arraylen_new];
                copy(randNum, (randNum+arraylen), temp1);
                delete [] randNum;
                randNum = temp1;

                copy(phrase, (phrase + arraylen), temp2);
                delete [] phrase;
                phrase = temp2;
                arraylen = arraylen_new;
            }
        }
        cout<<"test"<<endl;
        i++;

    }    
    randomTxt.close();

    /*for(int i = 0; i < arraylen;i++)
    {
        cout<< "UPC " << i << ": " << UPC[i] << "\t" << "Phrase " << i << ": " << phrase[i] << endl;

    }*/

    return 0;
}

检查i 的值时，打印输出如下：

0
0
0
test
test
2
2
2
test
test
4
4
4

依此类推，直到我的文件被完全读取。我的迭代需要正确匹配，因为我使用它将每一行保存到单独的数组中。任何想法为什么它似乎跳过了内部 while 循环？

这是文本文件的sn-p：

333331234567,blah,"this is nonsense"
222221234567,word,"yadda yadda words"
111111234567,thing,"total gibberish stuff"

Answer 1

我不会重现您的问题。

但我必须在您的示例代码中修复一些名称，所以也许我不小心修复了它？

这是我的版本，带有一些额外的 DEBUG 打印语句。

还请注意，检查eof()很少有用，因此将外部循环更改为while (getline(randomTxt, line))。

然后有了i循环索引，我认为写成for循环更自然。

Live On Coliru

#include <iostream>
#include <string>
#include <fstream>
#include <sstream>

/// returns: new array length

int main() {
    size_t arraylen = 7;
    std::string line;
    std::string *randNum = new std::string[arraylen];
    std::string *phrase  = new std::string[arraylen];

    std::ifstream randomTxt;

    randomTxt.open("random.txt");

    for (size_t i=0; getline(randomTxt, line); ++i)
    {
        std::cout << "DEBUG LINE: '" << line << "'\n";
        //nextstep = 0;

        std::stringstream ss(line);
        std::string field;
        while (getline(ss, field, ',')) {
            std::cout << "DEBUG INNER " << i << " '" << field << "'\n";

            if (i == (arraylen - 1)) {
                size_t arraylen_new = arraylen + 1;
                {
                    std::string *tmp = new std::string[arraylen_new];
                    copy(randNum, randNum + arraylen, tmp);
                    delete[] randNum;
                    randNum = tmp;
                }

                {
                    std::string *tmp = new std::string[arraylen_new];
                    copy(phrase, (phrase + arraylen), tmp);
                    delete[] phrase;
                    phrase = tmp;
                }
                arraylen = arraylen_new;
            }
        }
    }
}

打印

DEBUG LINE: '333331234567,blah,"this is nonsense"'
DEBUG INNER 0 '333331234567'
DEBUG INNER 0 'blah'
DEBUG INNER 0 '"this is nonsense"'
DEBUG LINE: '222221234567,word,"yadda yadda words"'
DEBUG INNER 1 '222221234567'
DEBUG INNER 1 'word'
DEBUG INNER 1 '"yadda yadda words"'
DEBUG LINE: '111111234567,thing,"total gibberish stuff"'
DEBUG INNER 2 '111111234567'
DEBUG INNER 2 'thing'
DEBUG INNER 2 '"total gibberish stuff"'

注意事项

• 您可能需要创建一个 grow_array 函数，因为您复制了该代码
• 您可能希望按因子增长，而不是一次增长 1 个元素；这根本不会扩展并导致糟糕的性能/堆碎片