【小梦C嘎嘎——启航篇】string介绍以及日常使用的接口演示

   
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C语言中的字符串

C语言中，字符串是以’\0’结尾的一些字符的集合，为了操作方便，C标准库中提供了一些str系列的库函数，但是这些库函数与字符串是分离开的，不太符合OOP的思想，而且底层空间需要用户自己管理，稍不留神可
能还会越界访问。

标准库中的string类

1. string是表示字符串的字符串类
2. 该类的接口与常规容器的接口基本相同，再添加了一些专门用来操作string的常规操作。
3. string在底层实际是：basic_string模板类的别名，typedef basic_string<char, char_traits, allocator> string;
4. 不能操作多字节或者变长字符的序列。在使用string类时，必须包含#include头文件以及using namespace std;

string 比较常使用的接口

对上述函数和其他函数的测试代码演示：

#include<iostream>
#include<string>
using namespace std;void Teststring1()
{string s1;string s2("hello bit");string s3(s2);string s4(s2.begin(), s2. end());s1 = "abcdef";cout << s1 << endl;cout << s2 << endl;cout << s3 << endl;cout << s4<< endl;}void test_string3()
{string s1("hello world");string s2 = "hello world";for (size_t i = 0; i < s1.size(); i++){cout << s1[i] << " ";}cout << endl;string::iterator it = s1.begin();while (it != s1.end()){cout << *it << " ";it++;}cout << endl;for (auto ch : s2){cout << ch << " ";}cout << endl;
}void func(const string & s)
{//string::const_iterator it = s.begin();//auto it = s.begin();//while (it != s.end())//{//	//*it = 'a';//	cout << *it << " ";//	it++;//}//cout << endl;//string::const_reverse_iterator rit = s.rbegin();/*auto rit = s.rbegin();while (rit != s.rend()){cout << *rit << " ";++rit;}cout << endl;*/auto rit = s.rbegin();while (rit != s.rend()){cout << *rit << " ";++rit;}cout << endl;
}void test_string4()
{string s1("hello world");string s2 = "hello world";func(s1);}void test_string5()
{string s1("hello worldxxxxxxxxxxxxxxxxxxxxxxxxxxyyyyyyyyyyyyyyyyyy");string s2(s1);cout << s2 << endl;string s3(s1, 6, 5);cout << s3 << endl;string s4(s1, 6, 3);cout << s4 << endl;string s5(s1, 6);cout << s5 << endl;string s6(s1, 6, s1.size() - 6);cout << s6 << endl;string s7(10, 'a');cout << s7 << endl;string s8(++s7.begin(), --s7.end());cout << s8 << endl;s8 = s7;s8 = "xxx";s8 = 'y';
}void test_string6()
{string s1("hello world");string s2 = "hello world";cout << s1.size() << endl;cout << s1.capacity() << endl;s1.clear();cout << s1.size() << endl;cout << s1.capacity() << endl;}void test_string7()
{string s;/*s.reserve(100);for (auto ch : s){cout << ch << " ";}cout << endl;s.push_back('x');s.push_back('x');s.push_back('x');s.push_back('x');s += 'n';s += "bit helloc";for (auto ch : s){cout << ch;}cout << endl;*///size_t old = s.capacity();//cout << "初始" << s.capacity() << endl;//for (size_t i = 0; i < 100; i++)//{//	s.push_back('x');//	if (s.capacity() != old)//	{//		cout << "扩容:" << s.capacity() << endl;//		old = s.capacity();//	}//}//s.reserve(10);//cout << s.capacity() << endl;s = "hello bit";cout << s.size() << endl;cout << s.capacity() << endl;s.resize(10, 'a');cout << s << endl;cout << s.size() << endl;cout << s.capacity() << endl;}void test_string8()
{string s = "hello";s.append(" bit");cout << s << endl;string s3 = "hello";string s2;s2 = s3 + " bit";cout << s2 << endl;s2 += s2;cout << s2 << endl;//s += '#';//s += "hello";//s += ss;//cout << s << endl;//string ret1 = ss + '#';//string ret2 = ss + "hello";//cout << ret1 << endl;//cout << ret2 << endl;
}void test_string9()
{std::string str("xxxxxxx");std::string base = "The quick brown fox jumps over a lazy dog.";str.assign(base);std::cout << str << '\n';str.assign(base, 5, 10);std::cout << str << '\n';
}void test_string10()
{// 空格替换为20%std::string s2("The quick brown fox jumps over a lazy dog.");string s3;for (auto ch : s2){if (ch != ' '){s3 += ch;}else{s3 += "%20";}}for (auto ch : s3){cout << ch;}cout << endl;printf("s2：%p\n", s2.c_str());printf("s3：%p\n", s3.c_str());swap(s2, s3);//s2.swap(s3);printf("s2：%p\n", s2.c_str());printf("s3：%p\n", s3.c_str());
}void test_string11()
{string s1("test.cpp.tar.zip");//size_t i = s1.find('.');size_t i = s1.rfind('.');string s2 = s1.substr(i);cout << s2 << endl;//string s3("https://legacy.cplusplus.com/reference/string/string/rfind/");//string s3("ftp://www.baidu.com/?tn=65081411_1_oem_dg");string s3("https://leetcode.cn/problems/first-unique-character-in-a-string/submissions/");// 协议      https// 域名      leetcode.cn// 资源名    problems/first-unique-character-in-a-string/submissions/string sub1, sub2, sub3;i = s3.find(':');sub1 = s3.substr(0, i);cout << sub1 << endl;size_t len  = s3.find('/', i + 3);sub2 = s3.substr(i + 3, len - (i + 3));cout << sub2 << endl;sub3 = s3.substr(len + 1);cout << sub3 << endl;
}void test_string12()
{std::string str("Please, replace the vowels in this sentence by asterisks.");std::size_t found = str.find_first_not_of("abc");while (found != std::string::npos){str[found] = '*';found = str.find_first_not_of("abcdefg", found + 1);}std::cout << str << '\n';/*std::string str("Please, replace the vowels in this sentence by asterisks.");std::size_t found = str.find_first_of("abcd");while (found != std::string::npos){str[found] = '*';found = str.find_first_of("abcd", found + 1);}std::cout << str << '\n';*/}int main()
{/*string s1, s2;cin >> s1 >> s2;cout << s1 << endl;cout << s2 << endl;*/string str;//cin >> str;getline(cin, str, '!');cout << str;/*size_t i = str.rfind(' ');if (i != string::npos){cout << str.size() - (i + 1) << endl;}else{cout << str.size() << endl;}*///Teststring1();//test_string2();//test_string3();//test_string4();//test_string5();//test_string6();//test_string7();//test_string8();//test_string9();//test_string11();//test_string12();return 0;
}

总结撒花💞

   本篇文章旨在分享的是string 使用知识。希望大家通过阅读此文有所收获！
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