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title: Boost学习笔记5 - Boost::StringAlgorithms
mathjax: true
date: 2020-03-17 19:56:26
categories: [c++笔记,Boost学习笔记]
tags: [c++笔记,Boost学习笔记]
keywords: [c++笔记,Boost学习笔记]
StringAlgorithms
我终于找到一个暂时没有被编入C++17的库了，听说在C++20中他也没进，哈哈哈。
大小写转化
首先上来的肯定就是大小写转化啦，使用函数to_upper_copy(string)就可以了。
#include <boost/algorithm/string.hpp>
#include <iostream>
int main() {
std::string s = "abcdefgABCDEFG";
std::cout << boost::algorithm::to_upper_copy(s) << std::endl;
std::cout << boost::algorithm::to_lower_copy(s) << std::endl;
}
删除子串
erase_all_copy就是说先copy一份，然后再将子串全部删除，如果不带copy就是说直接操作穿进去的母串。下面的代码都可以去掉_copy,erase_first指的是删除第一次出现的，last指的是删除最后一次出现的，nth指的是删除第n次出现的，n从0开始,erase_head值的是删除前n个字符，erase_tail指的是删除后n个字符。
#include <boost/algorithm/string.hpp>
#include <iostream>
int main() {
std::string s = "000111000111ababab000111000111";
std::cout << s << std::endl;
// boost::algorithm::erase_all(s,"ab");
std::cout << boost::algorithm::erase_all_copy(s, "ab") << std::endl;
std::cout << boost::algorithm::erase_first_copy(s, "111") << std::endl;
std::cout << boost::algorithm::erase_last_copy(s, "111") << std::endl;
std::cout << boost::algorithm::erase_nth_copy(s, "111",0) << std::endl;
std::cout << boost::algorithm::erase_nth_copy(s, "111",100) << std::endl;
std::cout << boost::algorithm::erase_head_copy(s, 4) << std::endl;
std::cout << boost::algorithm::erase_tail_copy(s, 4) << std::endl;
}
查找子串
find一类的函数，同上,他将返回一个iterator_range的迭代器。这个迭代器可以操作子串。注意子串和母串共享空间。
#include <boost/algorithm/string.hpp>
#include <iostream>
int main() {
std::string s = "000111000111ababab000111000111";
std::cout << s << std::endl;
auto x = boost::algorithm::find_first(s,"000");
x[0] = '2';
std::cout << s << std::endl;
//std::cout << boost::algorithm::find_last(s, "111") << std::endl;
}
又是一套代码下来了
#include <boost/algorithm/string.hpp>
#include <iostream>
int main() {
std::string s = "000111000111ababab000111000111";
std::cout << s << std::endl;
auto x = boost::algorithm::find_first(s,"000");
x = boost::algorithm::find_last(s,"1");
x = boost::algorithm::find_nth(s,"1",3);
x = boost::algorithm::find_tail(s,3);
x = boost::algorithm::find_head(s,3);
std::cout << s << std::endl;
//std::cout << boost::algorithm::find_last(s, "111") << std::endl;
}
替换子串
replace又是一套如下
#include <boost/algorithm/string.hpp>
#include <iostream>
int main() {
std::string s = "000111000111ababab000111000111";
std::cout << s << std::endl;
// boost::algorithm::replace_all(s,"ab");
std::cout << boost::algorithm::replace_all_copy(s, "ab","all") << std::endl;
std::cout << boost::algorithm::replace_first_copy(s, "111","first") << std::endl;
std::cout << boost::algorithm::replace_last_copy(s, "111","last") << std::endl;
std::cout << boost::algorithm::replace_nth_copy(s, "111", 0,"nth") << std::endl;
std::cout << boost::algorithm::replace_nth_copy(s, "111", 100,"nth") << std::endl;
std::cout << boost::algorithm::replace_head_copy(s, 2,"Head") << std::endl;
std::cout << boost::algorithm::replace_tail_copy(s, 2,"Tail") << std::endl;
}
修剪字符串
trim_left_copy 指的是从左边开始修建，删掉空字符等，trim_right_copy是从右边开始修建，trim_copy是两边一起修剪。
#include <boost/algorithm/string.hpp>
#include <iostream>
int main() {
std::string s = "\t ab d d d d d \t";
std::cout << "|" << s << "|" << std::endl;
std::cout << "|" << boost::algorithm::trim_left_copy(s) << "|" << std::endl;
std::cout << "|" << boost::algorithm::trim_right_copy(s) << "|" << std::endl;
std::cout << "|" << boost::algorithm::trim_copy(s) << "|" << std::endl;
}
这个代码输出了
| ab d d d d d |
|ab d d d d d |
| ab d d d d d|
|ab d d d d d|
我们还可以通过指定谓词来修剪使用trim_left_copy_if
#include <boost/algorithm/string.hpp>
#include <iostream>
int main() {
std::string s = " 01 0 1 000ab d d d d d 11111111";
std::cout << "|" << s << "|" << std::endl;
std::cout << "|" << boost::algorithm::trim_left_copy_if(s,boost::algorithm::is_any_of(" 01")) << "|" << std::endl;
std::cout << "|" << boost::algorithm::trim_right_copy_if(s,boost::algorithm::is_any_of(" 01")) << "|" << std::endl;
std::cout << "|" << boost::algorithm::trim_copy_if(s,boost::algorithm::is_any_of(" 01")) << "|" << std::endl;
}
更多的谓词,我们还有is_lower、is_upper、is_space等谓词。
#include <boost/algorithm/string.hpp>
#include <iostream>
int main() {
std::string s = " 01 0 1 000ab d d d d d 11111111";
std::cout << "|" << s << "|" << std::endl;
std::cout << "|" << boost::algorithm::trim_copy_if(s,boost::algorithm::is_space()) << "|" << std::endl;
std::cout << "|" << boost::algorithm::trim_copy_if(s,boost::algorithm::is_digit()) << "|" << std::endl<<std::endl;
s = "aaaBBBaBBaaa";
std::cout << "|" << s << "|" << std::endl;
std::cout << "|" << boost::algorithm::trim_copy_if(s,boost::algorithm::is_lower()) << "|" << std::endl;
}
字符串比较
starts_with(s,t)判断s是否以t开头，类似的有ends_with,contains,lexicographical_compare分别表示s是否以t结尾，s是否包含t，s与t的字典序比较。
#include <boost/algorithm/string.hpp>
#include <iostream>
int main() {
std::cout << boost::algorithm::starts_with("abcde", "abc") << std::endl;
std::cout << boost::algorithm::ends_with("abcde", "cde") << std::endl;
std::cout << boost::algorithm::contains("abcde", "cde") << std::endl;
std::cout << boost::algorithm::lexicographical_compare("abcde", "cde") << std::endl;
std::cout << boost::algorithm::lexicographical_compare("abcde", "abcde") << std::endl;
std::cout << boost::algorithm::lexicographical_compare("cde", "abcde") << std::endl;
}
字符串分割
这个就简单多了，直接split+谓词函数就行了
#include <boost/algorithm/string.hpp>
#include <iostream>
int main() {
std::string s = "abc abc abc * abc ( abc )";
std::vector<std::string> v;
boost::algorithm::split(v, s, boost::algorithm::is_any_of(" *()"));
for (auto x : v) std::cout << x << ".";
std::cout << std::endl;
}
输出
abc.abc.abc...abc...abc...
我们注意看有些函数前面有个i，比如ierase_all, 这个说的是忽略大小写。