Unique set of words from string C++

Question

I am trying to write a function that inputs an array_string and finds unique words, then copies them over to unique_array. This is a bit over my head I feel like and need some advice on where to go from here..

void unique140(string str_array[], int array_size, string unique_array[], int&unique_size)
{
  int i = 0;
  int j = 0;

for(i = 0; i < array_size; i++)
{
  for(j = 0; j < unique_size; j++)
  if (str_array[i] != unique_array[j])
  {unique_array[i];}
  if(str_array[i] == unique_array[j]
  break;
 }

Answer 1

Try something like:

void unique140(string str_array[], int array_size, 
                 string unique_array[], int&unique_size)
{
    unordered_map<string,int> count;
    for(int i=0; i<array_size; i++) {
        count[str_array[i]]++;
    }
    unique_size = 0;
    for(auto it=count.begin(); it!=count.end(); ++it) {
        if(it->second==1) {
            unique_array[unique_size++] = it->first;
        }
    }
}

use a std::map if you dont have a std::unordered_map.

Answer 2

You're not a million miles away, the loops look good. Now you have to use those loops to make a decision, is the word str_array[i] present in the unique_array or not? Now just a minutes thought will tell you that str_array[i] is present if any one of the equality tests str_array[i] == unique_array[j] is true. Here's how to code that

for(i = 0; i < array_size; i++)
{
    bool in_unique_array = false;
    for(j = 0; j < unique_size; j++)
       if (str_array[i] == unique_array[j])
           in_unique_array = true;
    ...
}

Next we have to add str_array[i] to unique_array if it's not already there. So that's

for(i = 0; i < array_size; i++)
{
    bool in_unique_array = false;
    for(j = 0; j < unique_size; j++)
       if (str_array[i] == unique_array[j])
           in_unique_array = true;
    if (!in_unique_array)
    {
        ...
    }
}

Finally having decided to add the string to unique_array we have to do that

for(i = 0; i < array_size; i++)
{
    bool in_unique_array = false;
    for(j = 0; j < unique_size; j++)
       if (str_array[i] == unique_array[j])
           in_unique_array = true;
    if (!in_unique_array)
    {
        unique_array[unique_size] = str_array[i];
        unique_size++;
    }
}