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Preface
Continue today. Yesterday, I did nothing to summarize the vector container. Today I saw the string container made some time ago, and I wanted to summarize this part, just to review the knowledge of the string container.
One, the basic concept of string
1. Essence:
string is a C++ style string, and string is essentially a class.
2. The difference between string and char* .
Char is a pointer.
String is a class, which encapsulates char*, manages this string, and is a char* type container.
3. Features
Many member methods are encapsulated inside the string class.
For example: find find, copy copy, delete delete, replace replace, insert insert.
String manages the memory allocated by char*, don't worry about copying out of bounds and value out of bounds, etc., it is the responsibility of the class.
Two, string constructor
1. Constructor prototype:
string(); 创建一个空的字符串 例如：string str;
string(const char* s); 使用字符串s初始化
string(const string& str); 使用一个string对象初始化另一个string对象
string(int n,char c); 使用n个字符c初始化
2. The code example is as follows:
#include<iostream>
using namespace std;
#include<string>
//string的构造函数
/*
string(); //创建一个空的字符串 例如：string str;
string(const char* s); //使字符串s初始化
string(const string& str); //使用一个string对象初始化另一个string对象
string(int n,char c); //使用n个字符初始化
*/
void test01()
{
string s1;//默认构造
const char* str="hello world";
string s2(str);
cout<<"s2= "<<s2<<endl;
string s3(s2);
cout<<"s3= "<<s3<<endl;
string s4(10,'a');
cout<<"s4= "<<s4<<endl;
}
int main()
{
test01();
system("pause");
return 0;
}
Three, string assignment operation
1. Function description:
Assign value to string
2. Function prototype for assignment
string& operator=(const char* s); char*类型字符串赋值给当前的字符串
string& operator=(const string &s); 把字符串s赋值给当前的字符串
string& operator=(char c); 字符赋值给当前的字符串
string& assign(const char *s); 把字符串s赋值给当前的字符串
string& assign(const char *s,int n); 把字符串s的前n个字符赋值给当前的字符串
string& assign(const string &s); 把字符串s赋给当前字符串
string& assign(int n,char c); 用n个字符c赋值给当前字符
3. Code demonstration
#include<iostream>
using namespace std;
#include<string>
/*
string& operator=(const char* s); char*类型字符串 赋值给当前的字符串
string& operator=(const string &s); 把字符串s赋给当前的字符串
string& operator=(char c); 字符赋值给当前字符串
string& assign(const char*s); 把字符串s赋值给当前的字符串
string& assign(const char*s,int n); 把字符串s的前n个字符赋值给当前的字符串
string& assign(const string &s); 把字符串s赋值给当前字符串
string& assign(int n,char c); 用n个字符c赋给当前字符串
*/
void test01()
{
string str1; //定义一个 字符串
str1="hello world"; //char*类型字符串 赋值给当前的字符串str1
cout<<"str1= "<<str1<<endl;
string str2;
str2=str1;//把字符串s赋给当前的字符串
cout<<"str2= "<<str2<<endl;
string str3;
str3='a';//字符赋值给当前字符串
cout<<"str3= "<<str3<<endl;
string str4;
str4.assign("hello C++");//把字符串s赋值给当前的字符串
cout<<"str4= "<<str4<<endl;
string str5;
str5.assign("hello C++",8);//把字符串s的前n个字符赋值给当前的字符串
cout<<"str5= "<<str5<<endl;
string str6;
str6.assign(str5);//把字符串s赋值给当前字符串str5d的赋值给str6
cout<<"str6= "<<str6<<endl;
string str7;
str7.assign(10,'w');// 用n个字符c赋给当前字符串
cout<<"str7= "<<str7<<endl;
}
int main()
{
test01();
system("pause");
return 0;
}
Four, string string splicing
1. Function description:
realize the splicing of strings at the end of the string
2. Function prototype:
string& operator+=(const char* str); 重载+=操作符
string& operator+=(const char c); 重载+=操作符
string& operator+=(const string& str); 重载+=操作符
string& append(const char *s); 把字符串s连接到当前字符串结尾
string& append(const char *s,int n); 把字符串s的前n个字符串连接到当前字符串结尾
string& append(const string &s); 同operator+=（const string& str）
string& append(const string &s,int pos,int n); 字符串s中从pos开始的n个字符连接到字符串结尾
3. Code example
#include<iostream>
using namespace std;
#include<string>
//功能：实现在字符串末尾拼接字符串
//函数原型：
/*
string& operator+=（const char* str）; //重载+=操作符
string& operator+=(const char c); //重载+=操作符
string& operator+=(const string& str); //重载+=操作符
string& append(const char *s); //把字符串s连接到当前字符串结尾
string& append(const char*s,int n); //把字符串s的前n个字符连接到当前字符串结尾
string& append(const string &s); //同operator+=(const string& str)
string& append(const string &s,int pos,int n); //字符串s中从pos开始的n个字符连接到字符串结尾
*/
void test01()
{
string str1="我";
str1+="爱学习";//重载+=操作符,对str1进行拼接
cout<<"str1= "<<str1<<endl;
str1+=":";//重载+=操作符,对str1进行拼接
cout<<"str1="<<str1<<endl;
string str2="C++ 概率论 英语 树莓派";
str1+=str2;//利用+=在str1后面加一个str2
cout<<"str1= "<<str1<<endl;
string str3="I";
str3.append("LOVE");//使用append来进行拼接在str3后拼接
cout<<"str3= "<<str3<<endl;
str3.append("study cpp",5);
cout<<"str3= "<<str3<<endl;
//str3.append(str2);
//str3.append(str2,0,3); //只截取到C++
str3.append(str2,4,6);//只截取到概率论，参数2从那个位置开始截取，参数3结束位置，若参数3小于参数2则只截取一个
//I LOVE GAME LOL DNF
cout<<"str3= "<<str3<<endl;
}
int main()
{
test01();
system("pause");
return 0;
}
Five, String find and replace
1. Function description:
Search: find whether the specified string exists or not
Replace: replace the string at the specified position
2. Function prototype:
int find(const string& str,int pos=0) const; 查找str第一次出现位置.从pos开始查找
int find(const char* s,int pos=0) const; 查找s第一次出现位置.从pos开始查找
int find(const char* s,int pos,int n) const; 从pos位置查找s的前n个字符第一次位置
int find(const char c,int pos =0) const; 查找字符c第一次出现位置
int rfind(const string& str,int pos=npos) const; 查找str最后一次位置.从pos开始查找
int rfind(const char* s,int pos=npos) const; 查找s最后一次出现位置.从pos开始查找
int rfind(const char* s,int pos,int n) const; 从pos查找s的前n个字符最后一次位置
int rfind(const char c,int pos=0) const; 查找字符c最后一次出现位置
string& replace(int pos,int n,const string& str); 替换从pos开始n个字符为字符串str
string& replace(int pos,int n,const char* s); 替换从pos开始的n个字符为字符串s
3. Code example
#include<iostream>
using namespace std;
#include<string>
void test01()
{
string str1="abcdefde";
int pos=str1.find("de");
if(pos==-1)
{
cout<<"未找到字符串"<<endl;
}
else
{
cout<<"找到字符串，pos= "<<pos<<endl;
}
//rfind和find区别
//rfind从右往左查找 find从左向右查找
pos=str1.rfind("de");
cout<<"pos= "<<pos<<endl;
}
//2、替换
void test02()
{
string str1="abcdef";
//从1号位置起3个字符 替换为“1111”
str1.replace(1,3,"1111");
cout<<"str1="<<str1<<endl;
}
int main()
{
test01();
test02();
system("pause");
return 0;
}
Six, string string comparison
1. Function description:
comparison between strings
2. Comparison method:
string comparison is based on character ASCII code comparison
= return 0
＞ return 1
＜ return -1
3. Function prototype:
int compare(const string &s) const; 与字符串s比较
int compare(const char *s) const; 与字符串s比较
4. Code example:
#include<iostream>
using namespace std;
#include<string>
//功能描述：字符串比较
void test01()
{
string str1="hello";
string str2="xello";
if(str1.compare(str2)==0)
{
cout<<"str1 等于 str2"<<endl;
}
else if(str1.compare(str2)>0)
{
cout<<"str1大于str2"<<endl;
}
else
{
cout<<"str1小于str2"<<endl;
}
}
int main()
{
test01();
system("pause");
return 0;
}
Seven, string character acquisition
1. Function prototype:
There are two ways to obtain a single character in string
char& operator[](int n); 通过[]方式取字符
char& at(int n); 通过at方法获取字符
2. Code demonstration example:
#include<iostream>
using namespace std;
#include<string>
void test01()
{
string str="hello";
cout<<"str"<<str<<endl;
//1、通过[]访问单个字符
for(int i=0;i< str.size();i++)
{
cout<<str[i]<<" ";
}
cout<<endl;
//2、通过at方式访问单个字符
for(int i=0;i< str.size();i++)
{
cout<<str.at(i)<<" ";
}
cout<<endl;
//3、修改单个字符
str[0]='x';//第0号字符修改
//xello
cout<<"str= "<<str<<endl;
//xxllo
str.at(1)='x';
cout<<"str= "<<str<<endl;
}
int main()
{
test01();
system("pause");
return 0;
}
Eight, String insertion and deletion
1. Function description:
Insert and delete characters in string
2. Function prototype:
string& insert(int pos,const char* s); 插入字符
string& insert(int pos,const string& str); 插入字符串
string& insert(int pos,int n,char c); 在指定位置插入n个字符c
string& erase(int pos,int n = npos); 删除从pos开始的n个字符
3. Code example:
#include<iostream>
using namespace std;
#include<string>
void test01()
{
string str="hello";
//插入
str.insert(1,"111");
//jlllello
cout<<"str= "<<str<<endl;
//删除
str.erase(1,3);
cout<<"str= "<<str<<endl;
}
int main()
{
test01();
system("pause");
return 0;
}
Nine, string substring
1. Function description:
get the desired string from the string
2. Function prototype:
string substr(int pos=0,int n=npos) const; 返回由pos开始的n个字符组成的字符串
3. Code example:
#include<iostream>
using namespace std;
#include<string>
//string字串
void test01()
{
string str ="abcdef";
string subStr=str.substr(1,3);//str.来点出来
cout<<"sunStr= "<<subStr<<endl;
}
//使用操作
void test02()
{
string email="[email protected]";
//从邮件地址中 获取 用户信息
int pos=email.find("@");//8
cout<<pos<<endl;
string usrName=email.substr(0,pos);
cout<<usrName<<endl;
}
int main()
{
test01();
system("pause");
return 0;
}
to sum up
The above is the knowledge of the string container I saw, the basic concept of string, string constructor, string assignment operation, string string splicing, String search and replacement, string string comparison, string character acquisition, String insertion and deletion, string substring, etc. . I have learned a lot from the review and I have to continue to learn C++ ( ￣▽￣ )ブ.