C++【string】用法和例子

 /***
  * string 基础api复习
  * 8 AUG 2018
  */

 #include <iostream>
 #include <string>
 using namespace std;

 void print(string str, int index)
 {
     std::cout << "str" << index << " = " << str << std::endl;
 }

 int main()
 {
     // string对象初始化
     string str0("i am a boy~");
     string str1 = "hello world!";
     string str2(str1);
     string str3(, 'c');
     string str4(str1, , ); // 从【2】索引起始，长度为3的字符串

     print(str0, );
     print(str1, );
     print(str2, );
     print(str3, );
     print(str4, );

     // string相关简单函数
     bool power;
     int str_len;
     char te_ch;
     string te_str;
     power = str0.empty();   // 判断字符串是否为空
     std::cout << "power = " << power << std::endl;
     str_len = str1.size();  // 字符串长度
     std::cout << "str_len = " << str_len << std::endl;
     te_ch = str2[];        // 返回字符串的第n个字符，下标从0开始
     std::cout << "str2[4] = " << te_ch << std::endl;
     te_ch = str2.at();     // 返回字符串的第n个字符，下标从0开始,同上
     std::cout << "str2.at(4) = " << te_ch << std::endl;
     te_str = str1 + str0;   // 连接两个字符串变成一个新的字符串
     std::cout << "str1 + str0 = " << te_str << std::endl;
     te_str = str3;          // 替换字符串
     std::cout << "te_str = " << te_str << std::endl;
     te_str.append(str0);    // 追加字符串
     std::cout << "te_str = " << te_str << std::endl;
     te_str.assign(str0);    // 为字符串对象赋值
     std::cout << "te_str = " << te_str << std::endl;

     // str.begin()&&str.end()均为迭代器
     string::iterator it = str0.begin();    // 字符串迭代器，类似指针
     std::cout << "it = " << (*it) << std::endl;

     // string::c_str()
     char* char_str = new char[strlen(str0.c_str()) + ];
     strcpy(char_str, str0.c_str());        // 当需要将字符串转成const char*时，用c_str(意味着转换成C语音的方式)
     std::cout << "char_str = " << char_str << std::endl;
     delete []char_str;
     char_str = NULL;

     // string::erase()，注意，erase后迭代器自动指向后一个位置
     str0.erase(, );                                // 从index值为5.删除长度为4个字符
     std::cout << "str0.erase(5, 2) = " << str0 << std::endl;
     str0.erase(str0.begin() + );                    // 删除index值为2的字符
     std::cout << "str0.erase(str0.begin() + 2) = " << str0 << std::endl;
     str0.erase(str0.begin() + , str0.end() - );   // 从index值为2，删除到index末尾减一
     std::cout << "str0.erase(str0.begin() + 2) = " << str0 << std::endl;

     // string::find()
     std::size_t found = str1.find(str4, );         // 从str1中找str4第一次出现的地方
     if (found != string::npos)
         std::cout << "first found is " << found << std::endl;
     found = str1.find('o');                         // 从str1中找o第一次出现的地方
     if (found != string::npos)
         std::cout << "first found is " << found << std::endl;
     found = str1.find("world");                     // 从str1中找world第一次出现的地方
     if (found != string::npos)
         std::cout << "first found is " << found << std::endl;    

     // string::insert()
     str0.insert(, " love");        // 在str0的index值为1后插入 love
     print(str0, );
     str0.insert(, " you", , );   // 在str0的index值为6后插入 you中从index值为0到长度为3的字符串
     print(str0, );
     str0.insert(, str1);           // 在str0的index值为0后插入str1
     print(str0, );

     // string::length()与string::size()用法相同，值也一样
     std::cout << "str0.length() = " << str0.length() << " str0.size() = " << str0.size() << std::endl;

     // string::maxsize()返回能够存储字符串的最大长度
     std::cout << "str0.max_size() = " << str0.max_size() << std::endl;

     // string::rbegin()和string::rend()逆向迭代器
     for (string::reverse_iterator it = str0.rbegin(); it != str0.rend(); it++)
     {
         std::cout << (*it);
     }
     std::cout << std::endl;
     print(str0, );

     // 这个是algorithm里面的，混入是为了对比效果
     reverse(str0.begin(), str0.end());
     print(str0, );

     // string::replace()用法类似string::insert()
     str0.replace(, , "ni hao", , );
     print(str0, );

     // string::substr()
     te_str = str0.substr(, );
     std::cout << "te_str = " << te_str << std::endl;

     // string::swap()
     te_str.swap(str0);
     print(str0, );
     std::cout << "te_str = " << te_str << std::endl;

     while (true)
     {
         getchar();
     }
     return ;
 }