1648. Sell Diminishing-Valued Colored Balls

Description

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.

 

Constraints:

• n == code.length
• 1 <= n <= 100
• 1 <= code[i] <= 100
• -(n - 1) <= k <= n - 1

 

Solutions

Solution: Sliding Window

• Time complexity: O(n)
• Space complexity: O(n)

 

JavaScript

/**
 * @param {number[]} code
 * @param {number} k
 * @return {number[]}
 */
const decrypt = function (code, k) {
  const n = code.length;
  const result = Array.from({ length: n }, () => 0);

  if (k === 0) return result;

  let start = k > 0 ? 1 : n + k;
  let end = k > 0 ? k : n - 1;
  let sum = 0;

  for (let index = start; index <= end; index++) {
    sum += code[index];
  }

  for (let index = 0; index < n; index++) {
    result[index] = sum;
    sum -= code[start];
    start = (start + 1) % n;
    end = (end + 1) % n;
    sum += code[end];
  }
  return result;
};