In practice, the string series in c ++ -- initialization, deletion, and Case sensitivity of string (construct erase upper-lower)

In practice, the string series in c ++ -- initialization, deletion, and Case sensitivity of string (construct erase upper-lower)

The string has an iterator design pattern, and I have not yet realized the benefits brought by the iterator. Many times I can use methods similar to array indexes to complete the task.

Scenario 1: Delete all uppercase letters of a string
Here the erase method is used:

#include
  
     #include
   
      #include
    
       using namespace std;  int main()  {    string str = "This IS A  trick";      for(string::iterator iter = str.begin();  iter != str.end();++iter){            if(isupper(*iter)){             str.erase(iter);             --iter;        }    }   for(string::iterator iter = str.begin();    iter != str.end();++iter)    cout<<*iter<<" ";   return 0;  }  
    
   
  

The above code will be wrong, because the previous blog "unescaped pitfalls-after erase is used by vector, the iterator becomes a wild Pointer" said, that is, the position pointed by the iterator after erase.

Scenario 2: initialize a string
I have discussed the initialization of string in my blog:

#include
  
   #include
   
    using namespace std;int main(){    string s = "0123456789abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz" + 'A';    int t = 'A';    string s1 = "0123456789abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz" + t;    cout << t << endl;    cout << s << endl;    cout << s1 << endl;    return 0;}
   
  

The output result is unexpected:
65
Tuvwxyz
Tuvwxyz

Note that the difference between character and string should be clarified. Do not write double quotation marks as single quotation marks.
Cause:
Convert char type to integer type
Const char * pointer offset pointer passed to the string Constructor

Scenario 3: uppercase/lowercase letters in string
The general for loop will not be written, and a seldom used one will be written directly:

# Include
  
   
# Include using namespace std; int main () {string str = "heLLo"; // It may not contain
   
    
Transform (str. begin (), str. end (), str. begin (), toupper); cout <
    
     
Cout <
     
    
   
  

Note that cout cannot directly output a string.
This leads to an important topic. It does not contain the string header file. Can it be used as a string object? Can it be used as a string object or a string object?
I guess this is why the standard library is constantly updated, and to be compatible with earlier versions