tallying elements in an array

So, I'm trying to tally the elements of an array. By this I mean, I have a large array, and开发者_Python百科 each element will have multiples of itself throughout the array. I am trying to figure out how many times each element occurs, however I keep running into the issue of there being duplicate tallies. Since "x" could exist at 12 different places in the array, when I loop through it and keep a running sum, I get the tally for "x" 12 different times. Does anyone know of a simpler/better way to keep a tally of an array with no duplicates?

My code is:

where count is the number of elements

    for(i=0;i<count;i++)
    {


            for(x=0; x<count;x++)
            {
                    if(array[i]==array[x])
                    {
                            tallyz++;
                    }   

            }

                    tally[i]=tallyz-1;
                    tallyz=0;
                    }

    }

std::map<X, unsigned> tally;

for(i = 0; i < count; ++i)
    ++tally[array[i]];

Note that this is best if the redundancy in the array is fairly high. If most items are unique you're probably better just sorting the array as others have mentioned.

If you can sort the array, simply sort it. Then all you have left is a linear scan of the elements, checking if the element behind this one is the same as the current element (don't forget bounds checking).

As an alternative to sorting, you could use a map:

template<class T, size_t N>
void printSums(T (array&)[N]) {
  map<T, size_t> m;
  for(T*p = array; p < array+N; ++p) {
    ++m[*p];
  }
  for(map<T,size_t>::iterator it = m.begin(); it != m.end(); ++it) {
    cout << it->first << ": " << it->second << "\n";
  }
}

Warning: this is untested code.

first use a map just as John said,then traverse the tally array:

std::map<X, unsigned> data;

for(i = 0; i < count; i++)
    data[array[i]]++;

for(i = 0; i < count; i++)
    tally[i]=data[tally[i]]-1;