我如何将空字符串存储到向量中

Question

我是C ++的新手，无法用定界符分割字符串并将子字符串放入向量中。

我的代码如下：

vector<string> split(const string &s, const string &delim)
{   
    string::size_type pos = s.find_first_of(delim,0);
    int start = 0;
    vector<string> tokens;

    while(start < s.size())
    {
            if(start++ != pos + 1)
                    tokens.push_back(" ");
            pos = s.find_first_of(delim, start);
            tokens.push_back(s.substr(start, pos - start));
    }

    for(vector<string>::size_type i = 0; i != tokens.size(); ++i)
            cout << tokens[i];

    return tokens;
}

将字符串和定界符传递到函数中并执行拆分。 假定此函数将空字符串放入向量中，但对我而言不这样做。

例如，如果我在main中将函数调用为：

int main()
{
   split("<ab><>cd<", "<>");
}

输出应该是

"","ab","","","","cd",""

减去引号

但是我的代码的输出当前是

ab b    cd d  

任何帮助，将不胜感激。

Answer 1

这样就可以了...

#include <iostream>
#include <vector>

using namespace std;

vector<string> split(string record, string token) {
    vector<string> results;
    size_t startPos = 0;
    size_t pos = 0;

    // Step: If either argument is empty then return
    // an empty vector.
    if (record.length() == 0 || token.length() == 0) {
        return results;
    }

    // Step: Go through the record and split up the data.
    while(startPos < record.length()) {
        pos = record.find(token, startPos);
        if (pos == string::npos) {
            break;
        }

        results.push_back(record.substr(startPos, pos - startPos));
        startPos = pos + token.length();
    }

    // Step: Get the last (or only bit).
    results.push_back(record.substr(startPos, record.length() - startPos));

    // Step: Return the results of the split.
    return results;
}

void printData(vector<string> list) {
    for(vector<string>::iterator it = list.begin(); it < list.end(); it++) {
        cout << *it << endl;
    }
}

int main(int argc, char** argv) {
    string record = "";
    string delim = "";

    if (argc == 3) {
        record = argv[1];
        delim = argv[2];
        printData(split(record,delim));
    } else {
        string record = "comma,delimited,data";
        string delim = ",";
        printData(split(record,delim));

        record = "One<--->Two<--->Three<--->Four";
        delim = "<--->";
        printData(split(record,delim));
    }
}

Answer 2

看来您的循环做得并不正确：您逐个字符地行走，在每次迭代中都start一个start前进。 我怀疑您实际上是想拥有一个当前位置，找到下一个定界符，将当前位置和定界符之间的字符串添加到结果中，并使当前位置成为定界符之后的字符：

for (std::string::size_type start(0); start != s.npos; )
{
    std::string::size_type end(s.find_first_of(delim, start));
    tokens.push_back(s.substr(start, end != s.npos? end - start: end));
    start = end != s.npos? end + 1: s.npos;
}