C++ 标准库 <string>
C++ 标准库
C++ 标准库(Standard Template Library, STL)是 C++ 的核心组成部分之一,提供了丰富的数据结构和算法。
在 C++ 中,字符串是由字符组成的序列。
要在 C++ 程序中使用
#include
#include
基本语法
std::string 类的基本语法如下:
声明字符串变量:
std::string str;
初始化字符串:
std::string str = “Hello, World!”;
使用 + 连接字符串:
std::string str1 = “Hello, “;
std::string str2 = “World!”;
std::string result = str1 + str2;
常用成员函数
std::string 类提供了许多成员函数来操作字符串,以下是一些常用的成员函数:
size():返回字符串的长度。
empty():检查字符串是否为空。
operator[]:通过索引访问字符串中的字符。
substr():获取子字符串。
find():查找子字符串在主字符串中的位置。
replace():替换字符串中的某些字符。
实例
下面是一个使用
实例
#include
#include
int main() {
// 声明并初始化字符串
std::string greeting = “Hello, World!”;
std::cout << “Greeting: “ << greeting << std::endl;
// 使用 size() 获取字符串长度
std::cout << “Length of the greeting: “ << greeting.size() << std::endl;
// 使用 empty() 检查字符串是否为空
std::cout << “Is the greeting empty? “ << (greeting.empty() ? “Yes” : “No”) << std::endl;
// 使用 operator[] 访问特定位置的字符
std::cout << “Character at position 7: “ << greeting[7] << std::endl;
// 使用 substr() 获取子字符串
std::string sub = greeting.substr(7, 5);
std::cout << “Substring from position 7 with length 5: “ << sub << std::endl;
// 使用 find() 查找子字符串
std::cout << “Position of ‘World’ in the greeting: “ << greeting.find(“World”) << std::endl;
// 使用 replace() 替换字符串中的部分内容
// 替换 ‘World’ 为 ‘C++’
std::string modified = greeting;
std::string::size_type pos = modified.find(“World”);
if (pos != std::string::npos) {
modified.replace(pos, 5, “C++”); // 从位置 pos 开始,替换 5 个字符为 “C++”
}
std::cout << “Modified greeting: “ << modified << std::endl;
return 0;
}
输出结果:
Length of the greeting: 13
Is the greeting empty? No
Character at position 7: W
Substring from position 7 with length 5: World
Position of ‘World’ in the greeting: 7
Modified greeting: Hello, C++!std::string 成员函数汇总表
下面是一个常见的 std::string 成员函数的汇总:
函数名描述示例代码size()返回字符串的长度(字符数)。std::cout << str.size();length()与 size() 相同,返回字符串的长度。std::cout << str.length();empty()判断字符串是否为空。std::cout << (str.empty() ? “Yes” : “No”);operator[]访问字符串中指定位置的字符。std::cout << str[0];at()访问字符串中指定位置的字符(带边界检查)。std::cout << str.at(0);substr()返回从指定位置开始的子字符串。std::string sub = str.substr(0, 5);find()查找子字符串在字符串中的位置。std::cout << str.find(“sub”) << std::endl;rfind()从字符串末尾开始查找子字符串的位置。std::cout << str.rfind(“sub”) << std::endl;replace()替换字符串中的部分内容。str.replace(pos, length, “new_substring”);append()在字符串末尾添加内容。str.append(“ more”);insert()在指定位置插入内容。str.insert(pos, “inserted”);erase()删除指定位置的字符或子字符串。str.erase(pos, length);clear()清空字符串。str.clear();c_str()返回 C 风格的字符串(以 null 结尾)。const char* cstr = str.c_str();data()返回指向字符数据的指针(C++11 及之后的版本)。const char* data = str.data();compare()比较两个字符串。int result = str.compare(“other”);find_first_of()查找第一个匹配任意字符的位置。size_t pos = str.find_first_of(“aeiou”);find_last_of()查找最后一个匹配任意字符的位置。size_t pos = str.find_last_of(“aeiou”);find_first_not_of()查找第一个不匹配任意字符的位置。size_t pos = str.find_first_not_of(“aeiou”);find_last_not_of()查找最后一个不匹配任意字符的位置。size_t pos = str.find_last_not_of(“aeiou”);
实例
#include
#include
int main() {
std::string str = “Hello, World!”;
// size()
std::cout << “Length: “ << str.size() << std::endl;
// empty()
std::cout << “Is empty? “ << (str.empty() ? “Yes” : “No”) << std::endl;
// operator[]
std::cout << “First character: “ << str[0] << std::endl;
// at()
std::cout << “Character at position 7: “ << str.at(7) << std::endl;
// substr()
std::string sub = str.substr(7, 5);
std::cout << “Substring from position 7 with length 5: “ << sub << std::endl;
// find()
size_t pos = str.find(“World”);
std::cout << “Position of ‘World’: “ << pos << std::endl;
// replace()
str.replace(pos, 5, “C++”);
std::cout << “Modified string: “ << str << std::endl;
// append()
str.append(“ How are you?”);
std::cout << “Appended string: “ << str << std::endl;
// insert()
str.insert(7, “ Beautiful”);
std::cout << “String after insert: “ << str << std::endl;
// erase()
str.erase(7, 10);
std::cout << “String after erase: “ << str << std::endl;
// clear()
str.clear();
std::cout << “String after clear: “ << (str.empty() ? “Empty” : “Not empty”) << std::endl;
// c_str()
str = “Hello, C++!”;
const char* cstr = str.c_str();
std::cout << “C-style string: “ << cstr << std::endl;
// compare()
int cmp = str.compare(“Hello, C++!”);
std::cout << “Comparison result: “ << cmp << std::endl;
// find_first_of()
size_t pos_first_vowel = str.find_first_of(“aeiou”);
std::cout << “First vowel at position: “ << pos_first_vowel << std::endl;
// find_last_of()
size_t pos_last_vowel = str.find_last_of(“aeiou”);
std::cout << “Last vowel at position: “ << pos_last_vowel << std::endl;
// find_first_not_of()
size_t pos_first_non_vowel = str.find_first_not_of(“aeiou”);
std::cout << “First non-vowel at position: “ << pos_first_non_vowel << std::endl;
// find_last_not_of()
size_t pos_last_non_vowel = str.find_last_not_of(“aeiou”);
std::cout << “Last non-vowel at position: “ << pos_last_non_vowel << std::endl;
return 0;
}
输出结果:
Length: 13
Is empty? No
First character: H
Character at position 7: W
Substring from position 7 with length 5: World
Position of ‘World’: 7
Modified string: Hello, C++!
Appended string: Hello, C++! How are you?
String after insert: Hello, BeautifulC++! How are you?
String after erase: Hello, C++! How are you?
String after clear: Empty
C-style string: Hello, C++!
Comparison result: 0
First vowel at position: 1
Last vowel at position: 4
First non-vowel at position: 0
Last non-vowel at position: 10