So I am working on algorithms and I have this section where I can't figure out. Given a list of numbers, get the sum of consecutive values over 0 and add to new list. Expected result:

[1, 2, 3, 0, 1, 1, 1, 0, 2, 2, 2] == [6, 3, 6]

I have tried:

    for i in splitlist2:   
    if i == 0:
        resultlist.append((count2))
        count2 = 0
    else:
        count2  = i

Produces [6, 3]. I don't get why the last value is not appearing. Can someone please explain?

CodePudding user response：

def custom_sum(arr): 
    if not arr: return [] 
    res = [0] 
    for i, el in enumerate(arr): 
        if el == 0: 
            if i != len(arr)-1: 
                res.append(0) 
        else:
            res[-1]  = el 
    return res

A quick test:

arr = [1, 2, 3, 0, 1, 1, 1, 0, 2, 2, 2]
custom_sum(arr)
[6, 3, 6]

The general algorithm:

1. If the input array is empty return empty array
2. Otherwise initialize a result array with a 0
3. Loop over the elements of the input array:
4. If the element is 0, check whether it's the last element. If it's the last element of the input array, ignore. Otherwise, add a zero to the result array for a new partition.
5. If the element is not zero, add its value to the last value in result array.

CodePudding user response：

from itertools import groupby

list1 = [1, 2, 3, 0, 1, 1, 1, 0, 2, 2, 2]
ans = []
arr = [list(v) for k,v in groupby(list1, key = lambda x: x != 0) if k != 0]
for i in arr:
    ans.append(sum(i))
print(ans)

Output :

[6,3,6]