Finding how many same strings are in an array:)

[matkenis]

Hey, so i came across this little problem today. I cant figure the best way to find how many same strings are in an array. I tried checking every second string if they are the same but thats not the way to go.

Note: I arranged them all in alphabetical order to make it easier to work with, but still i cant figure it out. Any IDEAS? :D

-Thanks!!:)

example:
string array[8] = {"AAA", "AAA", "AAA", "BBB", "BBB", "CCC", "DDD", "EEE"};

So there are 3 AAA's, 2 BBB's and 3 others. So all put together tehere are 5 diffrent strings.

[48T7M4Gy]

Since you started with them sorted it makes it easy to travel the list and at each change of value you can get the current count from the last change , reset count at change point and keep travelling, comparing last with current, and counting.

[Ericool]

there is data structures that takes duplicates , you can then called a method to get that count. do some search with the stl.

[TheIdeasMan]

Hi,


With the question, you had "how many same strings" at the beginning, but had " tehere are 5 diffrent strings." at the end.

So that is contradictory.

Seen as it is sorted, consider these:

This counts the A's and B's:

Starting at position 1 (the second item) if it is equal to the previous, increment a counter. Continue to the next item.

This counts the A's , B's C's D's E's:

Starting at position 1 (the second item) if it is not equal to the previous, increment a counter. Continue to the next item.

[JLBorges]

#include <iostream>
#include <string>
#include <algorithm>
#include <iterator>
#include <iomanip>

int main()
{
    std::string names[] = { "AAA", "AAA", "AAA", "BBB", "BBB", "AAA", "CCC", "DDD", "BBB", "EEE", "CCC" };
    const std::size_t N = sizeof(names) / sizeof(*names) ;

    // sort the names
    // http://en.cppreference.com/w/cpp/algorithm/sort
    std::sort( names, names+N ) ;

    std::size_t n_unique_strings = 1 ; // the first string is unique

    for( std::size_t i = 1 ; i < N ; ++i ) // start with the second string
    {
        if( names[i] != names[i-1] ) // if this string is not equal to the previous string
            ++n_unique_strings ; // we have found a unique string
    }
    std::cout << "1. #unique strings: " << n_unique_strings << '\n' ;


    // remove duplicate strings (move unique strings to the front of the sorted names)
    // http://en.cppreference.com/w/cpp/algorithm/unique
    // note: the duplicated strings are move to the back and trashed (they may contain unspecified values)
    const auto end_of_unique_strings = std::unique( names, names+N ) ;

    std::cout << "2. #unique strings: " << end_of_unique_strings - names << " the unique strings are: " ;
    for( auto iter = names ; iter != end_of_unique_strings ; ++iter )
        std::cout << std::quoted(*iter) << ' ' ;
    std::cout << '\n' ;
}

http://coliru.stacked-crooked.com/a/602b71243dc5f908

[matkenis]

@JLBorges
Wow, thanks. I'll check this, for sure! :))