是什么

string response = "hello world";
string findMe = "world";

if(response.find(findMe) != string::npos)
{
     //found
}

实际上，你可以尝试使用boost库，我认为std::string没有提供足够的方法来做所有常见的字符串操作。在boost中，你可以只使用boost::algorithm::包含:

#include <string>
#include <boost/algorithm/string.hpp>

int main() {
    std::string s("gengjiawen");
    std::string t("geng");
    bool b = boost::algorithm::contains(s, t);
    std::cout << b << std::endl;
    return 0;
}

如果该功能对您的系统至关重要，那么使用旧的strstr方法实际上是有益的。算法中的std::search方法是最慢的。我的猜测是，创建这些迭代器需要很多时间。

我用来计时的代码是

#include <string>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <random>
#include <chrono>

std::string randomString( size_t len );

int main(int argc, char* argv[])
{
        using namespace std::chrono;

        const size_t haystacksCount = 200000;
        std::string haystacks[haystacksCount];
        std::string needle = "hello";

        bool sink = true;

        high_resolution_clock::time_point start, end;
        duration<double> timespan;

        int sizes[10] = { 10, 20, 40, 80, 160, 320, 640, 1280, 5120, 10240 };

        for(int s=0; s<10; ++s)
        {
                std::cout << std::endl << "Generating " << haystacksCount << " random haystacks of size " << sizes[s] << std::endl;
                for(size_t i=0; i<haystacksCount; ++i)
                {
                        haystacks[i] = randomString(sizes[s]);
                }

                std::cout << "Starting std::string.find approach" << std::endl;
                start = high_resolution_clock::now();
                for(size_t i=0; i<haystacksCount; ++i)
                {
                        if(haystacks[i].find(needle) != std::string::npos)
                        {
                                sink = !sink; // useless action
                        }
                }
                end = high_resolution_clock::now();
                timespan = duration_cast<duration<double>>(end-start);
                std::cout << "Processing of " << haystacksCount << " elements took " << timespan.count() << " seconds." << std::endl;

                std::cout << "Starting strstr approach" << std::endl;
                start = high_resolution_clock::now();
                for(size_t i=0; i<haystacksCount; ++i)
                {
                        if(strstr(haystacks[i].c_str(), needle.c_str()))
                        {
                                sink = !sink; // useless action
                        }
                }
                end = high_resolution_clock::now();
                timespan = duration_cast<duration<double>>(end-start);
                std::cout << "Processing of " << haystacksCount << " elements took " << timespan.count() << " seconds." << std::endl;

                std::cout << "Starting std::search approach" << std::endl;
                start = high_resolution_clock::now();
                for(size_t i=0; i<haystacksCount; ++i)
                {
                        if(std::search(haystacks[i].begin(), haystacks[i].end(), needle.begin(), needle.end()) != haystacks[i].end())
                        {
                                sink = !sink; // useless action
                        }
                }
                end = high_resolution_clock::now();
                timespan = duration_cast<duration<double>>(end-start);
                std::cout << "Processing of " << haystacksCount << " elements took " << timespan.count() << " seconds." << std::endl;
        }

        return 0;
}

std::string randomString( size_t len)
{
        static const char charset[] = "abcdefghijklmnopqrstuvwxyz";
        static const int charsetLen = sizeof(charset) - 1;
        static std::default_random_engine rng(std::random_device{}());
        static std::uniform_int_distribution<> dist(0, charsetLen);
        auto randChar = [charset, &dist, &rng]() -> char
        {
                return charset[ dist(rng) ];
        };

        std::string result(len, 0);
        std::generate_n(result.begin(), len, randChar);
        return result;
}

在这里，我随机生成干草堆，并在其中搜索针。设置了草垛计数，但是每个草垛中的字符串长度从开始的10增加到最后的10240。程序大部分时间实际上是在生成随机字符串，但这是意料之中的。

输出结果为:

Generating 200000 random haystacks of size 10
Starting std::string.find approach
Processing of 200000 elements took 0.00358503 seconds.
Starting strstr approach
Processing of 200000 elements took 0.0022727 seconds.
Starting std::search approach
Processing of 200000 elements took 0.0346258 seconds.

Generating 200000 random haystacks of size 20
Starting std::string.find approach
Processing of 200000 elements took 0.00480959 seconds.
Starting strstr approach
Processing of 200000 elements took 0.00236199 seconds.
Starting std::search approach
Processing of 200000 elements took 0.0586416 seconds.

Generating 200000 random haystacks of size 40
Starting std::string.find approach
Processing of 200000 elements took 0.0082571 seconds.
Starting strstr approach
Processing of 200000 elements took 0.00341435 seconds.
Starting std::search approach
Processing of 200000 elements took 0.0952996 seconds.

Generating 200000 random haystacks of size 80
Starting std::string.find approach
Processing of 200000 elements took 0.0148288 seconds.
Starting strstr approach
Processing of 200000 elements took 0.00399263 seconds.
Starting std::search approach
Processing of 200000 elements took 0.175945 seconds.

Generating 200000 random haystacks of size 160
Starting std::string.find approach
Processing of 200000 elements took 0.0293496 seconds.
Starting strstr approach
Processing of 200000 elements took 0.00504251 seconds.
Starting std::search approach
Processing of 200000 elements took 0.343452 seconds.

Generating 200000 random haystacks of size 320
Starting std::string.find approach
Processing of 200000 elements took 0.0522893 seconds.
Starting strstr approach
Processing of 200000 elements took 0.00850485 seconds.
Starting std::search approach
Processing of 200000 elements took 0.64133 seconds.

Generating 200000 random haystacks of size 640
Starting std::string.find approach
Processing of 200000 elements took 0.102082 seconds.
Starting strstr approach
Processing of 200000 elements took 0.00925799 seconds.
Starting std::search approach
Processing of 200000 elements took 1.26321 seconds.

Generating 200000 random haystacks of size 1280
Starting std::string.find approach
Processing of 200000 elements took 0.208057 seconds.
Starting strstr approach
Processing of 200000 elements took 0.0105039 seconds.
Starting std::search approach
Processing of 200000 elements took 2.57404 seconds.

Generating 200000 random haystacks of size 5120
Starting std::string.find approach
Processing of 200000 elements took 0.798496 seconds.
Starting strstr approach
Processing of 200000 elements took 0.0137969 seconds.
Starting std::search approach
Processing of 200000 elements took 10.3573 seconds.

Generating 200000 random haystacks of size 10240
Starting std::string.find approach
Processing of 200000 elements took 1.58171 seconds.
Starting strstr approach
Processing of 200000 elements took 0.0143111 seconds.
Starting std::search approach
Processing of 200000 elements took 20.4163 seconds.

如果字符串的大小相对较大(数百字节或更多)，并且c++17可用，您可能需要使用Boyer-Moore-Horspool搜索器(示例来自cppreference.com):

#include <iostream>
#include <string>
#include <algorithm>
#include <functional>

int main()
{
    std::string in = "Lorem ipsum dolor sit amet, consectetur adipiscing elit,"
                     " sed do eiusmod tempor incididunt ut labore et dolore magna aliqua";
    std::string needle = "pisci";
    auto it = std::search(in.begin(), in.end(),
                   std::boyer_moore_searcher(
                       needle.begin(), needle.end()));
    if(it != in.end())
        std::cout << "The string " << needle << " found at offset "
                  << it - in.begin() << '\n';
    else
        std::cout << "The string " << needle << " not found\n";
}

使用std::regex_search也不错。让搜索更通用的垫脚石。下面是一个带有注释的例子。

//THE STRING IN WHICH THE SUBSTRING TO BE FOUND.
std::string testString = "Find Something In This Test String";

//THE SUBSTRING TO BE FOUND.
auto pattern{ "In This Test" };

//std::regex_constants::icase - TO IGNORE CASE.
auto rx = std::regex{ pattern,std::regex_constants::icase };

//SEARCH THE STRING.
bool isStrExists = std::regex_search(testString, rx);

需要包含#include <regex>

出于某种原因，假设输入字符串被观察到类似于“在这个示例字符串中查找一些东西”，并且有兴趣搜索“在这个测试中”或“在这个示例中”，那么可以通过简单地调整如下所示的模式来增强搜索。

//THE SUBSTRING TO BE FOUND.
auto pattern{ "In This (Test|Example)" };

你可以尝试使用find函数:

string str ("There are two needles in this haystack.");
string str2 ("needle");

if (str.find(str2) != string::npos) {
//.. found.
}