Question

如何从两个单词之间返回一个字符串？例如：

hello how are you doing today?

输出结果为：

diff

我一直很好奇我将如何做到这一点。

Answer 1

您可以使用std::string::substr

假设您分别知道"START"和"STOP"的长度为5和4，

你可以这样做：

std::string str = "STARThello how are you doing today?END";
const int startSize = 5;  //or perharps something like startString.size()
const int endSize = 4;    //or perharps something like stopString.size()
const int countSize = str.size() - (startSize + endSize);

std::string substring = str.substr(startSize, countSize);

Answer 2

对于std :: regex来说可能是个好例子，它是C ++ 11的一部分。

#include <iostream>
#include <string>
#include <regex>

int main()
{
    using namespace std::string_literals;

    auto start = "START"s;
    auto end = "END"s;

    std::regex base_regex(start + "(.*)" + end);

    auto example = "STARThello how are you doing today?END"s;

    std::smatch base_match;
    std::string matched;

    if (std::regex_match(example, base_match, base_regex)) {
        // The first sub_match is the whole string; the next
        // sub_match is the first parenthesized expression.
        if (base_match.size() == 2) {
            matched = base_match[1].str();
        }
    }
    std::cout << "example: \""<<example << "\"\n";
    std::cout << "matched: \""<<matched << "\"\n";

}

打印：

example: "STARThello how are you doing today?END"
matched: "hello how are you doing today?"

我所做的是创建一个程序，创建两个字符串，start和end，用作我的开始和结束匹配。然后我使用正则表达式字符串来查找它们，并匹配中间的任何内容（包括任何内容）。然后我使用regex_match查找表达式的匹配部分，并将匹配设置为匹配的字符串。

有关详细信息，请参阅 http://en.cppreference.com/w/cpp/regex 和 http://en.cppreference.com/w/cpp/regex/regex_search

从两个单词之间获取字符串？

2 个答案: