【C++】使用 list 与 string 实现基础字符串操作

一、字符串的基础操作

1.1 - startsWith

bool startsWith(const std::string& fullString, const std::string& starting)
{if (fullString.length() >= starting.length()) {return (0 == fullString.compare(0, starting.length(), starting));} else {return false;}
}

1.2 - endsWith

bool endsWith(const std::string& fullString, const std::string& ending) {if (fullString.length() >= ending.length()){return (0 == fullString.compare(fullString.length() - ending.length(), ending.length(), ending));}else{return false;}
}

1.3 - trim

用于移除字符串前后两端的空白符

// Function to trim whitespace from the beginning and end of a string
std::string trim(const std::string& str) {size_t first = str.find_first_not_of(" \t\n\r\f\v");// No non-whitespace charactersif (first == std::string::npos){    // 如果从头开始非空白符找不到，说明所有的字符都是空白符，因此全部去掉return "";  }size_t last = str.find_last_not_of(" \t\n\r\f\v");// 即便 last 为 string::npos substr 也会做处理。return str.substr(first, (last - first + 1));
}

或者

#include <algorithm>
#include <cctype>// 去除字符串左侧空白
static inline void ltrim(std::string &s) {s.erase(s.begin(), std::find_if(s.begin(), s.end(), [](unsigned char ch) {return !std::isspace(ch);}));
}// 去除字符串右侧空白
static inline void rtrim(std::string &s) {s.erase(std::find_if(s.rbegin(), s.rend(), [](unsigned char ch) {return !std::isspace(ch);}).base(), s.end());
}// 去除字符串两侧空白
static inline void trim(std::string &s) {ltrim(s);rtrim(s);
}

1.4 - indexOf

用于获取第一个子串的位置索引，如果找不到则返回 -1。

// Function to find the index of the first occurrence of a substring
int indexOf(const std::string& str, const std::string& substr)
{size_t pos = str.find(substr);return (pos != std::string::npos) ? static_cast<int>(pos) : -1;
}

1.5 - replaceAll

// 替换字符串中所有匹配的子字符串
void replaceAll(std::string& source, const std::string& from, const std::string& to)
{// 如果字符串为空则返回。if (from.empty()) { return; }size_t startPos = 0;while ((startPos = source.find(from, startPos)) != std::string::npos) {source.replace(startPos, from.length(), to);startPos += to.length(); // 在替换后移动过去新增的部分}
}

二、list 基础操作

2.1 - 遍历

2.1.1 - 使用迭代器访问

#include <iostream>
#include <list>
std::list<int> myList = {1, 2, 3, 4, 5};// 使用迭代器遍历 std::list
for (auto it = myList.begin(); it != myList.end(); ++it)
{std::cout << *it << " ";
}
std::cout << std::endl;

2.1.2 - 使用基于范围的 for 循环遍历

#include <iostream>
#include <list>
// 使用范围基 for 循环遍历 std::list
for (int elem : myList) 
{std::cout << elem << " ";
}
std::cout << std::endl;

2.1.3 - 使用标准算法库遍历

#include <iostream>
#include <list>
#include <algorithm> // for std::for_each
std::list<int> myList = {1, 2, 3, 4, 5};// 使用 std::for_each 遍历 std::list
std::for_each(myList.begin(), myList.end(), [](int elem) {std::cout << elem << " ";
});
std::cout << std::endl;

2.2 - 访问元素

访问第 N 个元素

#include <iostream>
#include <list>std::list<int> myList = {10, 20, 30, 40, 50};
int N = 3;  // 以 0 为起始索引，访问第 4 个元素
auto it = myList.begin();
std::advance(it, N);  // 使用 std::advance 前进到第 N 个元素if (it != myList.end()) {std::cout << "The element at index " << N << " is " << *it << std::endl;
} else {std::cout << "Index out of range." << std::endl;
}

2.3 - 删除元素

删除前 N 个元素

std::list<int> myList = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};int N = 3;  // 指定要删除的元素数量
if (N <= myList.size()) {// 获取开始到第 N 个元素的迭代器auto it = myList.begin();std::advance(it, N);  // 移动迭代器到第 N 个位置// 从开始到第 N 个元素进行删除myList.erase(myList.begin(), it);
}// 打印剩余的元素
for (int elem : myList) {std::cout << elem << " ";
}
std::cout << std::endl;

三、list<string>

3.1 - 移除所有空字符串元素

#include <iostream>
#include <list>
#include <string>// 创建并初始化一个 std::list<std::string>
std::list<std::string> strings = {"Hello", "", "World", "", "C++17", ""};
// 输出原始列表
std::cout << "Original list:" << std::endl;
for (const auto& str : strings)
{std::cout << "'" << str << "'" << std::endl;
}
// 移除所有空字符串
strings.remove_if([](const std::string& s) { return s.empty(); });
// 输出修改后的列表
std::cout << "\nList after removing empty strings:" << std::endl;
for (const auto& str : strings) {std::cout << "'" << str << "'" << std::endl;
}

3.2 - 遍历字符串并应用 trim

std::list<std::string> myStrings = {"  hello  ", "  world!  ", "  example  "};// 遍历列表并应用 trim 函数
for (std::string& str : myStrings) {trim(str);
}
// 打印修剪后的字符串列表
for (const auto& str : myStrings) {std::cout << '"' << str << '"' << std::endl;
}

3.3 - 移除连续的空白行

将多个连续的空白行替换为一个空白行

#include <iostream>
#include <list>
#include <string>
#include <iterator>void compressEmptyLines(std::list<std::string>& lines) {bool lastWasEmpty = false;for (auto it = lines.begin(); it != lines.end(); ) {// 检查当前行是否为空白（或只包含空格）bool isEmpty = it->find_first_not_of(" \t\n\v\f\r") == std::string::npos;if (isEmpty) {if (lastWasEmpty) {// 如果当前行是空的，并且上一行也是空的，删除当前行it = lines.erase(it);} else {// 如果当前行是空的，但上一行不是，保留这行并标记lastWasEmpty = true;++it;}} else {// 如果当前行不是空的，继续前进lastWasEmpty = false;++it;}}
}int main() {std::list<std::string> lines = {"Hello"," "," ","World","","","!"," ","End"};compressEmptyLines(lines);// 输出处理后的列表for (const auto& line : lines) {std::cout << '"' << line << '"' << std::endl;}return 0;
}