# Using an array

In these tutorials you are passed an array of numbers (all numbers are between 0 and 9), you must process it using another array.

## Contents

## Show the frequency of each digit

You can create an array with ten items - one for each digit (you may be sure that all numbers in x are between 0 and 9).

if x is the list [1,1,1,5,9,9] then the result will be freq 0 0 1 3 2 0 3 0 4 0 5 1 6 0 7 0 8 0 9 2

Print the frequency of each digit

## Show the number of different digits

If x is the list [1,1,1,5,9,9] then the result will be 3 because there are three different number (namely 1,5 and 9)

You can use the freq array created as above - then just count the number of non-zero elements using an accumulator:

int acc = 0; for (int i=0;i<freq.length;i++) if (freq[i]>0) acc++; System.out.println(acc);

Print the number of different digits

## Show the repeated digits

If x is the list [1,1,1,5,9,9] then the result will be 1 and 9 because 1 occurs more than once and 9 occurs twice.

You can use the freq array created as above - then just show the index when the freq is more than 1:

for (int i=0;i<freq.length;i++) if (freq[i]>1) System.out.println(i);

Print the repeated digits

## Show the missing digits

If x is the list [1,1,1,5,9,9] then the result will be 2 3 4 6 7 8 because these digits are not in the input list.

You can use the freq array created as above - then just print the indexes when the freq is 0:

for (int i=0;i<freq.length;i++) if (freq[i]==0) System.out.println(i);

Print the missing digits