Defuse the Bomb

Problem Statement:

You have a bomb to defuse, and your time is running out! Your informer will provide you with a circular array code of length of n and a key k.
To decrypt the code, you must replace every number. All the numbers are replaced simultaneously.
If k > 0, replace the ith number with the sum of the next k numbers.
If k < 0, replace the ith number with the sum of the previous k numbers.
If k == 0, replace the ith number with 0.
As code is circular, the next element of code[n-1] is code[0], and the previous element of code[0] is code[n-1].
Given the circular array code and an integer key k, return the decrypted code to defuse the bomb!

Example 1:
Input: code = [5,7,1,4], k = 3
Output: [12,10,16,13]
Explanation: Each number is replaced by the sum of the next 3 numbers. The decrypted code is [7+1+4, 1+4+5, 4+5+7, 5+7+1]. Notice that the numbers wrap around.

Example 2:
Input: code = [1,2,3,4], k = 0
Output: [0,0,0,0]
Explanation: When k is zero, the numbers are replaced by 0. 

Example 3:
Input: code = [2,4,9,3], k = -2
Output: [12,5,6,13]
Explanation: The decrypted code is [3+9, 2+3, 4+2, 9+4]. Notice that the numbers wrap around again. If k is negative, the sum is of the previous numbers.


Solution:
class Solution:
    def decrypt(self, code: List[int], k: int) -> List[int]:
        
        ######### O(N); O(2N)
        
        # get prefixsum of all elements in the code
        prefixsum=[]
        for i in range(2):
            for each in range(len(code)):
                if prefixsum:
                    prefixsum.append(prefixsum[-1]+code[each])
                else:
                    prefixsum.append(code[each])
        
        # k is positive, we can get the sum of next k elements by subtracting current index element and kth element from current index
        if k>0:
            for each in range(len(code)):
                start=each
                end=start+k
                diff=prefixsum[end]-prefixsum[start]
                code[each]=diff
        
        # k is negative, we can get the sum of previous k elements by subtracting previous index element and kth element backward from that index
       
        elif k<0:
            for each in range(len(code)):
                start=each+len(code)-1
                end=start-(-k)
                diff=prefixsum[start]-prefixsum[end]
                code[each]=diff
        
        # else return list of 0
        else:
            return [0]*len(code)
        return code