How Determine the number of repeated integers and their counts?

Question

I tried to write a program to determine the number of repeated integers in an array and their counts but the program outputs roughly fulse, so my question is what the problem in my code i do not want use any class , thanks.

for example :

Input: Enter array size: 11 Enter array elements: 13 34 22 4 499 4 22 18 4 1 1 Output: There are 3 repeated numbers: 22: 2 times 4: 3 times 1: 2 times

but my output is :

1:2 times 4:3 times 4:2 times 22:2 times

import java.util.Scanner;

public class repeated_elements {

    public static void main(String[] args) {
        Scanner input = new Scanner (System.in);
        // User Choose The Array Size
        System.out.println("Enter Array Size: ");
        int size = input.nextInt();

        // The Array
        int[]Array = new int[size];

        // Read The Array Elements From The User
        System.out.println("Enter Array Elements:");
        for(int i =0; i<size; i++){
            Array[i]=input.nextInt();
        }

        // Sorting The Array (Ascending Order)
        for(int j = 0; j<size; j++){

            int mini = Array[j];
            int mini_index = j;

            for(int i = j; i<size; i++){
                if(Array[i] < mini){
                    mini = Array[i];
                    mini_index = i; 
                }
            }
            int tmp = Array[j];
            Array[j] = Array[mini_index];
            Array[mini_index] = tmp;
        }

        // Count The Repeated Numbers
        for(int i=0; i<size; i++){

            int key = Array[i];
            int counter = 0;

            for(int j=i; j<size; j++){
                if(key == Array[j]){
                    counter++;
                }
            }

            if(counter > 1 ){
                System.out.println(Array[i]+":"+counter+" times ");
            }
        }
    }
}

Answer 1

When we take a key for finding the ocurrence, first we need to check whether it is already searched for occurence (eg.4). So i have kept the key in array without any duplicates and then start searching it. It can be easily done with collections methods..

public class RepeatedElements {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        // User Choose The Array Size
        System.out.println("Enter Array Size: ");
        int size = input.nextInt();

        // The Array
        int[] Array = new int[size];

        // Read The Array Elements From The User
        System.out.println("Enter Array Elements:");
        for (int i = 0; i < size; i++) {
            Array[i] = input.nextInt();
        }

        // Sorting The Array (Ascending Order)
        for (int j = 0; j < size; j++) {

            int mini = Array[j];
            int mini_index = j;

            for (int i = j; i < size; i++) {
                if (Array[i] < mini) {
                    mini = Array[i];
                    mini_index = i;
                }
            }
            int tmp = Array[j];
            Array[j] = Array[mini_index];
            Array[mini_index] = tmp;
        }
//      System.out.println("sorted array:"+Arrays.asList(Array));
        int key[] = new int[Array.length];
        int keylen = 0;
        // Count The Repeated Numbers
        for (int i = 0; i < size; i++) {


            int found = 0;
            int k;
            for ( k=0;k<keylen;k++){
                if (key[k]==Array[i]){
                    found=1;
                }
            }
//      11  System.out.println("k value"+k+"i value"+i);
            if (found==1)
                continue;//already counted
            else
                key[keylen]=Array[i];

            int counter = 0;

            for (int j = i; j < size; j++) {
                if (key[keylen] == Array[j]) {
                    counter++;
                }
            }
            keylen++;
            if (counter > 1) {
                System.out.println(Array[i] + ":" + counter + " times ");
            }
        }

    }
}

The output is attached in the screenshot.

Answer 2

instead of this piece of code :

   // Count The Repeated Numbers
    for(int i=0; i<size; i++){

        int key = Array[i];
        int counter = 0;

        for(int j=i; j<size; j++){
            if(key == Array[j]){
                counter++;
            }
        }

        if(counter > 1 ){
            System.out.println(Array[i]+":"+counter+" times ");
        }
    }

try this:

   // Count The Repeated Numbers
    for(int i=0; i<size; ){   //<--- note the removal of i++

        int key = Array[i];
        int counter = 0;

        for(int j=i; j<size; j++){
            if(key == Array[j]){
                counter++;
            }else{
                i=j;
                break;
            }
        }

        if(counter > 1 ){
            System.out.println(key+":"+counter+" times ");
        }
    }

the problem is you don't sync your i and j variable

so for an input like :

1 1 1 1

you will get

1:4
1:3
1:2

After the correction I tested the program and for input:

11
13 34 22 4 499 4 22 18 4 1 1

I get :

1:2 times 
4:3 times 
22:2 times

EDIT: AS @CabelB suggested. it'll worth while have a look at Map implementation as well.

Answer 3

You parse each time the whole array, so you have to skip already parsed items. Increment the i counter in last for by counter value:

if(counter > 1 ){
    System.out.println(Array[i]+":"+counter+" times ");
    i +=counter;
}

That should be enough, hope it helps

Answer 4

Your code seems to be ok, but for one small problem. When you are outputting the number of appearances, you are going through the entire array every time, regardless if the value currently being checked was already checked before. In short, for an input array of [1, 1, 1, 1, 2, 2, 2, 2, 3, 3], the output is 1:4 times, 1:3 times and 1:2 times and so on.

I think you need to separate the distinct values from the sorted array or at least make sure that you do not repeat the counting for values that have already been counted.

Answer 5

If I were you, I would solve this with Map and counting there, but your code corrected:

public class Rep {

public static void main(String[] args) {
    int[] input = {1,1,2,2,2,0};
    // User Choose The Array Size
    System.out.println("Enter Array Size: ");
    int size = input.length;

    // The Array
    int[]Array = new int[size];

    // Read The Array Elements From The User
    System.out.println("Enter Array Elements:");
    for(int i =0; i<size; i++){
        Array[i]=input[i];
    }

    // Sorting The Array (Ascending Order)
    for(int j = 0; j<size; j++){

        int mini = Array[j];
        int mini_index = j;

        for(int i = j; i<size; i++){
            if(Array[i] < mini){
                mini = Array[i];
                mini_index = i; 
            }
        }
        int tmp = Array[j];
        Array[j] = Array[mini_index];
        Array[mini_index] = tmp;
    }

    // Count The Repeated Numbers
    for(int i=0; i<size; i++){

        int key = Array[i];
        int counter = 0;

        for(int j=0; j<size; j++){
            if(key == Array[j]){
                counter++;
            }
        }

        if(counter > 0 ){
            System.out.println(Array[i]+":"+counter+" times ");
        }
    }
}

}