How to Sum Consecutives in Java

1
2
3
4
5
6
7
8
9

[1,4,4,4,0,4,3,3,1] # should return [1,12,0,4,6,1]

"""So as you can see sum of consecutives 1 is 1 
sum of 3 consecutives 4 is 12 
sum of 0... and sum of 2 
consecutives 3 is 6 ..."""

[1,1,7,7,3] # should return [2,14,3]
[-5,-5,7,7,12,0] # should return [-10,14,12,0]

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12

import java.util.*;
public class Consecutives {
    public static List<Integer> sumConsecutives(List<Integer> s) {
      int previous = Integer.MAX_VALUE;
      LinkedList<Integer> l = new LinkedList<>();
      for (Integer v: s){
         l.add(v == previous? l.pollLast() + v : v); 
         previous = v;
      }
      return l; 
    }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15

import java.util.ArrayList;
import java.util.List;
public class Consecutives {
    public static List<Integer> sumConsecutives(List<Integer> s) {
        List<Integer> accumulator = new ArrayList<>();
        for (int i = 0, sum = 0; i < s.size(); i++) {
            sum += s.get(i);
            if (i == s.size() - 1 || s.get(i) != s.get(i + 1)) {
                accumulator.add(sum);
                sum = 0;
            }
        }
        return accumulator;
    }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20

import java.util.*;
public class Consecutives {
    public static List<Integer> sumConsecutives(List<Integer> list) {
        List<Integer> result = new ArrayList<>();
        int sum = list.get(0);
        int i = 0;
        while (i < list.size()){
            if (i == list.size() - 1) {
                result.add(sum);
            } else if (list.get(i).equals(list.get(i + 1))) {
                sum += list.get(i);
            } else {
                result.add(sum);
                sum = list.get(i + 1);
            }
            i++;
        }
        return result;
    }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42

import static org.junit.Assert.*;
import java.util.Arrays;
import java.util.List;
import org.junit.Test;

public class ConsecutivesTest {

    @Test
    public void test() {
        System.out.println("Basic Tests");
        List<Integer> i = Arrays.asList(1,4,4,4,0,4,3,3,1);
        List<Integer> o = Arrays.asList(1,12,0,4,6,1);
        System.out.println("Input: {1,4,4,4,0,4,3,3,1}");
        assertEquals(o, Consecutives.sumConsecutives(i));
        i = Arrays.asList(-5,-5,7,7,12,0);
        o = Arrays.asList(-10,14,12,0);
        System.out.println("Input: {-5,-5,7,7,12,0}");
        assertEquals(o, Consecutives.sumConsecutives(i));
        i = Arrays.asList(1,1,7,7,3);
        o = Arrays.asList(2,14,3);
        System.out.println("Input: {1,1,7,7,3}");
        assertEquals(o, Consecutives.sumConsecutives(i));
        i = Arrays.asList(3,3,3,3,1);
        o = Arrays.asList(12, 1);
        System.out.println("Input: {3,3,3,3,1}");
        assertEquals(o, Consecutives.sumConsecutives(i));
        i = Arrays.asList(2,2,-4,4,5,5,6,6,6,6,6,1);
        o = Arrays.asList(4, -4, 4, 10, 30, 1);
        System.out.println("Input: {2,2,-4,4,5,5,6,6,6,6,6,1}");
        assertEquals(o, Consecutives.sumConsecutives(i));
        i = Arrays.asList(1,1,1,1,1,3);
        o = Arrays.asList(5, 3);
        System.out.println("Input: {1,1,1,1,1,3}");
        assertEquals(o, Consecutives.sumConsecutives(i));
        i = Arrays.asList(1,-1,-2,2,3,-3,4,-4);
        o = Arrays.asList(1, -1, -2, 2, 3, -3, 4, -4);
        System.out.println("Input: {1,-1,-2,2,3,-3,4,-4}");
        assertEquals(o, Consecutives.sumConsecutives(i));
        
    }

}