將矢量轉換爲字符串

Question

在C++中，將整數的矢量（即vector<int>）轉換爲字符串的最簡單方法是什麼？

Answer 1

也許std::ostream_iterator和std::ostringstream：

#include <vector> 
#include <string> 
#include <algorithm> 
#include <sstream> 
#include <iterator> 
#include <iostream> 

int main() 
{ 
    std::vector<int> vec; 
    vec.push_back(1); 
    vec.push_back(4); 
    vec.push_back(7); 
    vec.push_back(4); 
    vec.push_back(9); 
    vec.push_back(7); 

    std::ostringstream oss; 

    if (!vec.empty()) 
    { 
    // Convert all but the last element to avoid a trailing "," 
    std::copy(vec.begin(), vec.end()-1, 
     std::ostream_iterator<int>(oss, ",")); 

    // Now add the last element with no delimiter 
    oss << vec.back(); 
    } 

    std::cout << oss.str() << std::endl; 
} 

Answer 2

這裏是使用定製的輸出迭代的替代方案。這個例子對於空列表來說行爲正確。此示例演示如何創建自定義輸出迭代器，類似於std::ostream_iterator。

#include <iterator> 
#include <vector> 
#include <iostream> 
#include <sstream> 

struct CommaIterator 
: 
    public std::iterator<std::output_iterator_tag, void, void, void, void> 
{ 
    std::ostream *os; 
    std::string comma; 
    bool first; 

    CommaIterator(std::ostream& os, const std::string& comma) 
    : 
    os(&os), comma(comma), first(true) 
    { 
    } 

    CommaIterator& operator++() { return *this; } 
    CommaIterator& operator++(int) { return *this; } 
    CommaIterator& operator*() { return *this; } 
    template <class T> 
    CommaIterator& operator=(const T& t) { 
    if(first) 
     first = false; 
    else 
     *os << comma; 
    *os << t; 
    return *this; 
    } 
}; 

int main() { 
    // The vector to convert 
    std::vector<int> v(3,3); 

    // Convert vector to string 
    std::ostringstream oss; 
    std::copy(v.begin(), v.end(), CommaIterator(oss, ",")); 
    std::string result = oss.str(); 
    const char *c_result = result.c_str(); 

    // Display the result; 
    std::cout << c_result << "\n"; 
} 

Answer 3

我通常做這種方式...

#include <string> 
#include <vector> 

int main(int argc, char* argv[]) 
{ 
    std::vector<char> vec; 
    //... do something with vec 
    std::string str(vec.begin(), vec.end()); 
    //... do something with str 
    return 0; 
} 

Answer 4

template<typename T> 
string str(T begin, T end) 
{ 
    stringstream ss; 
    bool first = true; 
    for (; begin != end; begin++) 
    { 
     if (!first) 
      ss << ", "; 
     ss << *begin; 
     first = false; 
    } 
    return ss.str(); 
} 

這是STR功能，可以使整數變成一個字符串，而不是到什麼整數代表一個字符。也適用於雙打。