How to count the frequency of words in a string?

[abdalimran]

What is the best way to count the frequency of words in a string?

Sample Input:
I don't know the key to success but key failure is trying please everybody.

Sample Output:

Word          Frequency
I                1
don't            1
know             1
the              2
key              1
to               3
success          1
but              1
key              1
failure          1
is               1
trying           1
please           1
everybody        1 

Someone write the code for me please..

[mutexe]

Someone write the code for me please

No.

Create a map of <std::string, int> (your string and your frequency).
iterate over the your string. for each word you come across search your map for it.
1. If the string can not be found in your map, add it to you map and a set the frequency to one.
2. If the string can be found increment the corresponding frequency by one.

[abdalimran]

actually I am so beginner that I don't understand <map>.
can you be more specific please?

[keskiverto]

Did you look at the example program in:
http://www.cplusplus.com/reference/map/map/find/

Too bad, it makes assumptions (for simplicity). It has these lines:

std::cout << "a => " << mymap.find('a')->second << '\n';
std::cout << "c => " << mymap.find('c')->second << '\n';

They would crash, if the map doesn't have 'a' or 'c'.
They are safer like this:

auto it = mymap.find('a');
if ( mymap.end() != it ) {
  std::cout << "a => " << it->second << '\n';
}
it = mymap.find('c');
if ( mymap.end() != it ) {
  std::cout << "c => " << it->second << '\n';
}

Naturally, when a key is not found, it has to be added: http://www.cplusplus.com/reference/map/map/emplace/

It is somewhat of a leap to get into standard library, but it is worth the effort.