为什么用于解析我读取的行的内部循环每隔一次迭代就会通过外部读取循环跳过

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，因为我使用它来将行的每一部分保存到单独的数组中。知道为什么它似乎跳过内部 while 循环吗？

以下是文本文件的片段：

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

Answer 1

我不重现您的问题。

但是我不得不修复您的示例代码中的一些名称，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。

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

然后对于i循环索引，我认为编写为 for 循环会更自然。

住在科里鲁

#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;
            }
        }
    }
}

指纹

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"'

笔记

• 您可能想要创建一个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