Defuse The Bomb

PROBLEM

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.

SOLVING

Code

class Solution {
public:
  vector<int> decrypt(vector<int> &code, int k) {
    size_t len = code.size();
    vector<int> result(len, 0);

    if (k == 0)
      return result;
    if (k > 0)
      for (int i = 0; i < len; i++)
	for (int j = 1; j <= k; j++)
	  result[i] += code[(i + j) % len];
    else
      for (int i = 0; i < len; i++)
	for (int j = 1; j <= (-1 * k); j++)
	  result[i] += code[(i - j + len) % len];
    return result;
  }
};

PROBLEM