1, Basic use of string object
The string data type is provided in the C + + standard template library, which is specially used to process strings. String is a class. Variables of this type are called "string objects"
1. To use the string object in a program, you must include the header file string in the program, that is, at the beginning of the program, you need to add the following statement: ාinclude < string >
2. Declaring a string object is similar to declaring a normal variable in the following format: string variable name;
string str1; //statement string object str1，Value is empty string city="Beijing"; //statement string object city，And use string constants for initialization string str2=city; //statement string object str2，And use string variables for initialization cout<<"str1="<<str1<<"."<<endl; cout<<city<<","<<str2<<endl; //You can also use character array pairs string Variable to initialize. for example: char name[ ]="C++program"; string s1=name; //You can also declare a string Object array, that is, each element in the array is a string. For example: string citys[ ]={"Beijing","Shanghai","Tianjin","Chongqing"}; cout<<citys[1]<<endl; //output Shanghai，Array subscript starts at 0 cout<<sizeof(citys)/sizeof(string)<<endl; //Number of output array elements sizeof(string);//It's every string The size of the object, so sizeof(citys)/sizeof(string)Represents the number of array elements.
1. String connection: +
string s2="C++"; string s3="C"; cout<<"s2= "<<s2<<endl;//s2= C++ cout<<"s3= "<<s3<<endl;//s3= C cout<<s3+s2<<endl; //CC++
2. Empty string judgment: empty()
string str; //Uninitialized, empty string if(str.empty()){ cout<<"str is NULL."<<",length="<<str.length()<<endl;//str is NULL.,length=0 } else{ cout<<"str is not NULL."<<endl; }
3. Append string: append()
string str; //Uninitialized, empty string str=str.append("ABC").append("DEFG"); cout<<"str is "<<str<<",size="<<str.size()<<endl;//str is ABCDEFG,size=7
4. Character lookup: find()
string str; //Uninitialized, empty string str=str.append("ABC").append("DEFG"); cout<<"str is "<<str<<",size="<<str.size()<<endl;//str is ABCDEFG,size=7 const char *p=str.c_str(); cout<<"*p="<<*p<<endl;//*p=A cout<<"p="<<p<<endl;//p=ABCDEFG //1,find Function return jk stay s Subscript location in cout<<"find:"<<str.find("D")<<endl; //Find successful, find:3 cout<<"find:"<<str.find("F")<<endl; //Find successful, find:5 //2,Returns the first occurrence and last occurrence of a substring in the parent string. cout<<"find_first_of:"<< str.find_first_of("A")<<endl;//find_first_of:0 cout<<"find_last_of:"<< str.find_last_of("A")<<endl;//find_last_of:0 //3,Find the position of a substring after a given location //From string str Subscript 4 start, find string D ,return D stay str Subscript in cout<<"find:"<<str.find("D",4)<<endl; //Find failed:find:4294967295 //From string str Subscript 0 start, find string F ,return F stay str Subscript in cout<<"find:"<<str.find("F",0)<<endl; //Find successful, find:5
5. Character insertion: insert()
string str; //Uninitialized, empty string str=str.append("ABC").append("DEFG"); //4,String insertion string str1=str.insert(4,"123");//Insert from subscript 4 cout<<str1<<endl;//ABCD123EFG