Question

I need to write a function to find the mode of a array. I’m not good at coming up with algorithms however and I’m hoping someone else knows how to do this.

I know the size of the array and the values in each element, and I have the array sorted from least to greatest.

array would be passed to the mode function like

mode = findMode(arrayPointer, sizePointer);

UPDATE:

After reading the comments I’ve tried this

int findMode(int *arrPTR, const int *sizePTR)
{
    int most_found_element = arrPTR[0];
    int most_found_element_count = 0;
    int current_element = arrPTR[0];
    int current_element_count = 0;
    int count;
    for (count = 0; count < *sizePTR; count++)
    {
        if(count == arrPTR[count])
             current_element_count++;
        else if(current_element_count > most_found_element)
        {
            most_found_element = current_element;
            most_found_element_count = current_element_count;
        }
        current_element = count;
        current_element_count=1;
    }

    return most_found_element;
}

I’m still having problems grasping this algorithm though if anyone can sort me out.
I’ve never used vectors so don’t really understand the other examples.

Answer 1

set most_found_element to the first element in the array
set most_found_element_count to zero
set current_element to the first element of the array
set current_element_count to zero
for each element e in the array
    if e is the same as the current_element
        increase current_element_count by one
    else
        if current_element_count is greater than most_found_element_count
            set most_found_element to the current_element
            set most_found_element_count to current_element_count
        set current_element to e
        set current_element_count to one
if current_element_count is greater than most_found_element_count
    set most_found_element to the current_element
    set most_found_element_count to current_element_count
print most_found_element and most_found_element_count

I thought the names would explain it, but here we go:

When we start, no element has been found the most times
  so the "high-score" count is zero.
Also, the "current" value is the first, but we haven't looked at it yet 
  so we've seen it zero times so far
Then we go through each element one by one
  if it's the same as "current" value, 
     then add this to the number of times we've seen the current value.
  if we've reached the next value, we've counted all of the "current" value.
     if there was more of the current value than the "high-score"
        then the "high-score" is now the current value
     and since we reached a new value
        the new current value is the value we just reached
Now that we've seen all of the elements, we have to check the last one
  if there was more of the current value than the "high-score"
    then the "high-score" is now the current value
Now the "high-score" holds the one that was in the array the most times!

Also note: my original algorithm/code had a bug, we have to do an extra check of “current” after the loop ends, as it never finds “the one after the last”.