CODEWITHSUNDEEP
javaarrayscounting
Adam Amin
Adam Amin

Reputation: 1456

Count the occurrences of successive items in an array

Let's assume the items array consists of the following items {3.1, 3.1, 3.1, 3.2, 3.2, 3.3, 3.4, 3.4, 3.4, 3.4, 3.1, 3.1}

What I want is to count the occurrence of each item in the successive items such that:

3.1 = 3 
3.2 = 2
3.3 = 1
3.4 = 4
3.1 = 2

I wrote the following function:

private void displayItems(List<Double> items) {
        double current_item=0;
        for(int i=0; i<items.size(); i++) {
            int count=1;
            current_item = items.get(i);
            if(i != items.size()) {
                for(int j=i+1; j<items.size(); j++) {
                    double next_item = items.get(j);
                    if(current_item == next_item) {
                        count++;
                    }else {
                        break;
                    }
                }
                System.out.println("item value is " + current_item + " and count is " + count);
            }
        }
    }

I got the following result:

item value is 3.1 and count is 3
item value is 3.1 and count is 2
item value is 3.1 and count is 1
item value is 3.2 and count is 2
item value is 3.2 and count is 1
item value is 3.3 and count is 1
item value is 3.4 and count is 4
item value is 3.4 and count is 3
item value is 3.4 and count is 2
item value is 3.4 and count is 1
item value is 3.1 and count is 2
item value is 3.1 and count is 1

What can I do to show the results like the following:

item value is 3.1 and count is 3
item value is 3.2 and count is 2
item value is 3.3 and count is 1
item value is 3.4 and count is 4
item value is 3.1 and count is 2

Please not that I don't want to count the occurrence of each item in the entire array, I just want to count its occurrence in the successive items only.

Upvotes: 2

Views: 209

Answers (7)

Eshu
Eshu

Reputation: 519

I guess all the above answers are correct but I also wanted to try this with single loop so here it is with single loop:

import java.util.Arrays;
import java.util.List;

public class SuccessiveCount {

    public static void main(String[] args) {
        List<Double> list = Arrays.asList(3.1, 3.1, 3.1, 3.2, 3.2, 3.3, 3.4, 3.4, 3.4, 3.4, 3.1, 3.1);
        double prevValue = list.get(0);
        int count = 0;
        for(int i=0; i < list.size(); i++) {
            if(prevValue == list.get(i)) {
                count++;
            }else {
                System.out.println("item value is "+list.get(i-1)+ " and count is "+ count);
                prevValue = list.get(i);
                count = 1;
            }
            if(list.size() == (i+1)) {
                System.out.println("item value is "+list.get(i-1)+ " and count is "+ count);
            }
        }

    }

}

PS : If anyone wants to make it look more cleaner I am up for suggestions.

Upvotes: 1

Mohammad
Mohammad

Reputation: 737

I think this will give the expected result

int count = 1;
        for (int i = 0; i < arr.size(); i++) {
            if (i != 0) {
                if (arr.get(i) - arr.get(i - 1) == 0) {
                    count++;
                } else if (arr.get(i) - arr.get(i - 1) != 0) {
                    System.out.println("Item value is " + arr.get(i - 1) + " and count is " + count);
                    count = 1;
                }
            }
            if (arr.size() == i + 1) {
                System.out.println("Item value is " + arr.get(i) + " and count is " + count);
            }
        }

Upvotes: 0

zawhtut
zawhtut

Reputation: 8561

x[n-1]-x[n]==0

should be the formula.

public class SuccessiveCounter {
    public static void main(String[] args) throws Exception {
        double[] x = {3.1,3.1,3.1,3.2,3.2,3.1,3.1,3.4,3.4,3.1,3.1};

        for(int n=1,count = 1;n<x.length;n++){
            if(x[n-1]-x[n]==0){
                count++;
            }else{
                System.out.println(x[n]+" "+count);
                count = 1;
            }
        }
    }
}

Upvotes: 2

heethjain21
heethjain21

Reputation: 146

Here are the changes,

int dec = 0;
int inc = 0;
if(current_item == next_item) {
     count++;
     dec = count; //new line
}
else {
     break;
}
}
//new stuff from here, printing "inc" instead of "count" in print statement.
dec--;
inc++;
if(dec==0){
    System.out.println("item value is " + current_item + " and count is " + inc);
}

Upvotes: 0

Durga Reddy
Durga Reddy

Reputation: 101

Your code is iterating over the values which were already counted in the previous iterations. A small tweak in the logic works as expected.

private void displayItems(List<Double> items) {
        double current_item=0;
        for(int i=0; i<items.size(); i++) {
            int count=1;
            current_item = items.get(i);
            if(i != items.size()) {
                int j=i+1;
                for(; j<items.size(); j++) {
                    double next_item = items.get(j);
                    if(current_item == next_item) {
                        count++;
                    }else {
                        break;
                    }
                }
                System.out.println("item value is " + current_item + " and count is " + count);
                i = j-1;
            }
        }
    }

Upvotes: 2

Michael
Michael

Reputation: 44230

You can use a map to map the double to how many times it occurs. Then simply loop over the map to print the values.

private static void count(List<Double> numbers)
{
    final Map<Double, Integer> numberToOccurrences = new HashMap<>();
    for(Double num : numbers)
    {
        numberToOccurrences.putIfAbsent(num, 0);
        numberToOccurrences.compute(num, (k, occurrences) -> ++occurrences);
    }
    numberToOccurrences.forEach((num, occurrences) -> 
        System.out.println("Number " + num + " occurs " + occurrences + " times")
    );
}

A few uses of lambdas here which may be considered more advanced, but they often result in the the most concise solution.

Upvotes: 1

shadowforce100
shadowforce100

Reputation: 48

What about making an ArrayList<String>?

ArrayList<String> runs = new ArrayList<String>();

Then storing something like

runs.add(current_item + "," + count);

instead of your print line, Then going through the array list and split each string by the comma to get desired output.

While it may work it is probably not ideal, but still a possible solution.

EDIT: You would go through runs after the nested loop

Upvotes: 0

Related Questions