defuse-the-bomb.cc

#include <iostream>
#include <vector>
 
class Solution {
public:
  std::vector<int> decrypt(std::vector<int>& code, int k) {
    int N = code.size();
    std::vector<int> result(N, 0);
 
    if (k == 0) return result;
 
    for (int i = 0; i < N; ++i) {
      int sum = 0;
      if (k > 0) {
        for (int j = 1; j <= k; ++j) {
          sum += code[(i + j) % N];  // next k elements
        }
      } else {
        for (int j = 1; j <= -k; ++j) {
          sum += code[(i - j + N) % N];  // previous k elements
        }
      }
      result[i] = sum;
    }
 
    return result;
  }
};