Question

I am trying to solve this, but i don’t know how…

Values[10] = {1,1,4,4,2,3,3,2,1,3}

to print:

{1,2,3,4} or {1,4,2,3} (not sorted, any order, but distinct)

I also need to count the number of times each number has occurred, both without sort, new arrays or boolean methods or other data structures, please advise as i am stuck.

Is there a simple method i can use to just print the unique values/ distinct values ?

Answer 1

It can be accomplished if your are willing to destroy your current array. and you assume that the array is either of type Integer (so nullable) or if not there is some bound such as all int are poistive so you can use -1.

for(int i = 0;  i < values.length; i++){               //for entire array             

    Integer currVal = values[i];                       // select current value
    int count = 1;                                     // and set count to 1

    if(currVal != null){                               // if value not seen

        for( int j = i + 1; j < values.length; j++){   // for rest of array
            if(values[j] == currVal){                  // if same as current Value 
                values[j] = null;                      // mark as seen
                count++;                               // and count it 
            } 
        }
        System.out.print("Number : "  + currVal + "  Count : " + count + "\n");
                                                       //print information
    }
                                                       // if seen skip.
}

In plain english, Go through the array in 2 loops, roughly O(n^2) time.
Go to index i. If index has not yet been seen (is not null) then go through the rest of array, mark any indexs with same value as seen (make it null) and increment count varable. At end of loop print value and count. If Index has be seen (is null) skip and go to next index. At end of both loops all values will be left null.

Input : Values[] = {1,1,4,4,2,3,3,2,1,3}


Output : Values[] = {1,null,4,null,2,3,null,null,null,null}
          Number : 1 Count : 3
          Number : 4 Count : 2
          Number : 2 Count : 2
          Number : 3 Count : 3

Edit: corrected my mistake in output, pointed out by commenters.