[一杯咖啡求解决字符串操作问题] C++ 读入一个文件，搜索其中所有的 answer="foobar" 字段并输出其中所有 foobar

[spencerqiu]

高中狗，被家长禁写码好久，字符串完全撸不动啊 ...

奖励 10 元，第一位成功解决的同学得 ...

程序要能在 Linux 上运行 ...

样例输入

文件名： sample.in

文件内容样例如下：
<div class="row">
<div class="span10">
<p>Remember, the <strong>only thing</strong> before everything, is to have a dogma. A dogma is a list consists by DOs and DONTanswer="C"s. You make it, stick to it while adapt it to reality, question yourself from time to time: is everything on the list mutuallanswer="A"y exclanswer="B"usive and collectively eanswer="B"xanswer="C"hausive?</p>

<p>And there is a meta dogma for dogmas:</p>

<ul>
<li>Avoid emotional tactics</li>
<li>Every kindness counts</li>
<li>Gentleness is the ultimate strength</li>
</ul>

样例输出：

直接输出到屏幕
C
A
B
B
C

[phttc]

第一反应就是正则匹配下。。。

[spencerqiu]

哦，对附加一条，输入文字里可能有汉字，不知道有没有干扰 ...

不会再附加了...我知道你们痛恨改需求...

[zhjits]

// 我没学过 C++，随手写的：

#include <iostream>
#include <regex>
using namespace std;
int main()
{
string var;

std::cin >> var;

const regex r("answer=\"(.+?)\"");
const regex r2("\".*\"");
smatch sm, sm2;

auto params_it = std::sregex_iterator(var.cbegin(), var.cend(), r);
auto params_end = std::sregex_iterator();

while (params_it != params_end) {
auto param = params_it->str();
std::regex_match(param, sm, r);
std::cout << sm[1] << std::endl;
++params_it;
}

return 0;
}

[spencerqiu]

@zhjits
需要从文件里面读，是整个文件读到 EOF ，而不是只读一个字符串 ...

下一条回复改完留下支付宝吧~

[spencerqiu]

@spencerqiu
输入文件名： sample.in

[zhjits]

// https://gist.github.com/Jamesits/01abcb0e23b4a4ef53fc
// 支付宝我写 gist 下面评论了自己找，找不到就算啦

#include <iostream>
#include <regex>
#include <fstream>
#include <string>
using namespace std;
int main() {

std::ifstream ifs("sample.in");
std::string var((std::istreambuf_iterator<char>(ifs)),
(std::istreambuf_iterator<char>()));

const regex r("answer=\"(.+?)\"");
const regex r2("\".*\"");
smatch sm, sm2;

auto params_it = std::sregex_iterator(var.cbegin(), var.cend(), r);
auto params_end = std::sregex_iterator();

while (params_it != params_end) {
auto param = params_it->str();
std::regex_match(param, sm, r);
std::cout << sm[1] << std::endl;
++params_it;
}

return 0;
}

[skydiver]

@zhjits 这个 r2 是干嘛用的？

[zhjits]

@skydiver Gist 里面已经删了。我说了我不会 C++ 啊……

[spencerqiu]

@zhjits
已转， Thx !

[htfy96]

https://gist.github.com/htfy96/652836a4340aec265624

[ilotuo]

好吧 本来想练手 结果搞了 45 分钟
T.T
基础太弱了

[icedx]

https://gist.github.com/anonymous/fa18c4e544d1b72bfca1

泡杯面的时候写的 肯定有数组越界 就不管了

[Wonicon]

https://gist.github.com/Wonicon/3fcbb841701aaf16eb2d
假定行缓冲足够大, answer=".*"不会换行......

[msg7086]

又在重新发明 grep 了？

[j3399141]

std::fstream file("sample.in.txt", std::fstream::in);
std::stringstream stream;
stream << file.rdbuf();
file.close();

std::string input = stream.str();

std::regex pattern("answer=\"(.*?)\"");

std::sregex_token_iterator next(std::begin(input), std::end(input), pattern, 1);
std::sregex_token_iterator end;

while (next != end)
{
std::cout << *next++ << std::endl;
}

[j3399141]

/*
需求随便改
*/
#include <iostream>
#include <regex>
#include <fstream>
#include <sstream>

int main(void)
{
try
{
std::fstream file("sample.in.txt", std::fstream::in);
std::stringstream stream;
stream << file.rdbuf();
file.close();

std::string input = stream.str();

std::regex pattern("answer=\"(.*?)\"");

std::sregex_token_iterator next(std::begin(input), std::end(input), pattern, 1);
std::sregex_token_iterator end;

std::vector<std::string> result;
while (next != end)
{
result.push_back(*next++);
}

copy(std::begin(result), std::end(result), std::ostream_iterator<std::string>(std::cout, "\n"));
std::vector<std::string>().swap(result);
}
catch (const std::exception& exception)
{
std::cerr << exception.what() << std::endl;
}

system("PAUSE");
return EXIT_SUCCESS;
}

[virusdefender]

这种事就别麻烦 c++了吧

<script src="https://gist.github.com/virusdefender/f593cd34282c7876d433.js"></script>

[virusdefender]

https://gist.github.com/virusdefender/f593cd34282c7876d433

[sagnitude]

凑热闹来一个
#include <stdlib.h>

int main() {
system("cat text.txt | grep -Po 'answer=\"\\K[^\"]*'");
return 0;
}

[ryd994]

grep+lookaround 就行的事，没事写什么代码？