我如何將空字符串存儲到向量中

Question

我是C ++的新手，無法用定界符分割字符串並將子字符串放入向量中。

我的代碼如下：

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;
}

將字符串和定界符傳遞到函數中並執行拆分。 假定此函數將空字符串放入向量中，但對我而言不這樣做。

例如，如果我在main中將函數調用為：

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

輸出應該是

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

減去引號

但是我的代碼的輸出當前是

ab b    cd d  

任何幫助，將不勝感激。

Answer 1

這樣就可以了...

#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

看來您的循環做得並不正確：您逐個字符地行走，在每次迭代中都start一個start前進。 我懷疑您實際上是想擁有一個當前位置，找到下一個定界符，將當前位置和定界符之間的字符串添加到結果中，並使當前位置成為定界符之后的字符：

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;
}