如何迭代由空格分隔的单词组成的字符串中的单词?
注意,我对C字符串函数或那种字符操作/访问不感兴趣。比起效率,我更喜欢优雅。我当前的解决方案:
#include <iostream>
#include <sstream>
#include <string>
using namespace std;
int main() {
string s = "Somewhere down the road";
istringstream iss(s);
do {
string subs;
iss >> subs;
cout << "Substring: " << subs << endl;
} while (iss);
}
并不是说我们需要更多的答案,但这是我受到埃文·特兰启发后想到的。
std::vector <std::string> split(const string &input, auto delimiter, bool skipEmpty=true) {
/*
Splits a string at each delimiter and returns these strings as a string vector.
If the delimiter is not found then nothing is returned.
If skipEmpty is true then strings between delimiters that are 0 in length will be skipped.
*/
bool delimiterFound = false;
int pos=0, pPos=0;
std::vector <std::string> result;
while (true) {
pos = input.find(delimiter,pPos);
if (pos != std::string::npos) {
if (skipEmpty==false or pos-pPos > 0) // if empty values are to be kept or not
result.push_back(input.substr(pPos,pos-pPos));
delimiterFound = true;
} else {
if (pPos < input.length() and delimiterFound) {
if (skipEmpty==false or input.length()-pPos > 0) // if empty values are to be kept or not
result.push_back(input.substr(pPos,input.length()-pPos));
}
break;
}
pPos = pos+1;
}
return result;
}
虽然有一些答案提供了C++20解决方案,但自从发布以来,已经做了一些更改,并将其作为缺陷报告应用于C++20。正因为如此,解决方案变得更短、更好:
#include <iostream>
#include <ranges>
#include <string_view>
namespace views = std::views;
using str = std::string_view;
constexpr str text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit.";
auto splitByWords(str input) {
return input
| views::split(' ')
| views::transform([](auto &&r) -> str {
return {r.begin(), r.end()};
});
}
auto main() -> int {
for (str &&word : splitByWords(text)) {
std::cout << word << '\n';
}
}
到今天为止,它仍然只在GCC的主干分支(Godbolt链接)上可用。它基于两个更改:P1391迭代器构造函数用于std::string_view和P2210 DR修复std::views::split以保留范围类型。
在C++23中,不需要任何转换样板,因为P1989向std::string_view:添加了一个范围构造函数
#include <iostream>
#include <ranges>
#include <string_view>
namespace views = std::views;
constexpr std::string_view text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit.";
auto main() -> int {
for (std::string_view&& word : text | views::split(' ')) {
std::cout << word << '\n';
}
}
(螺栓连杆)
仅为方便:
template<class V, typename T>
bool in(const V &v, const T &el) {
return std::find(v.begin(), v.end(), el) != v.end();
}
基于多个分隔符的实际拆分:
std::vector<std::string> split(const std::string &s,
const std::vector<char> &delims) {
std::vector<std::string> res;
auto stuff = [&delims](char c) { return !in(delims, c); };
auto space = [&delims](char c) { return in(delims, c); };
auto first = std::find_if(s.begin(), s.end(), stuff);
while (first != s.end()) {
auto last = std::find_if(first, s.end(), space);
res.push_back(std::string(first, last));
first = std::find_if(last + 1, s.end(), stuff);
}
return res;
}
用法:
int main() {
std::string s = " aaa, bb cc ";
for (auto el: split(s, {' ', ','}))
std::cout << el << std::endl;
return 0;
}