Merge for 2048

Implement a function to merge a line of the 2048 game, as a left movement was request.

If you don't know the 2048 game, have a look at its official page on github by Gabriele Cirulli. Pay attention, it could be gravely addictive!

The problem here is implementing a Python 2.7 function that gets in input a list of integers, where each element is a power of 2, or zero that stands for an empty place. We should return another list, same size of the input one, where all the elements are shifted to the left and merged as required.

So, for instance, an input of [2, 0, 2, 4] should result in an output of [4, 4, 0, 0], since the twos merge in a four, that won't merge with the other four given that newly merged element can't be part of this operation.

Here is my solution:

def merge(line):
    result = [] # 1
    check = False # 2
    for cur in line: # 3
        if check and result[-1] == cur: # 4
            result[-1] *= 2
            check = False
        elif cur != 0: # 5
            result.append(cur)
            check = True
    
    while len(result) < len(line): # 6
        result.append(0)
    return result

1. The result list, initialized empty.
2. Flag that states if the current element could be merged. Since this depends on the previous element, it is initialized to false.
3. Loop on all the element in the input list. If the current one is zero, I don't have to do anything, just move to the next one.
4. Otherwise, if the current element could be merged, I check the last element inserted in the result list, if they match, I merge them, and I signal that no merge could be done on the next element.
5. Usually, I append the current element to the result list, signal that a merge with the next element is possible, and continue looping.
6. The problem requires that the output list has the same size of the input one.