1652. Defuse the Bomb

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

Rust Solution

struct Solution;

impl Solution {
    fn decrypt(code: Vec<i32>, k: i32) -> Vec<i32> {
        let n = code.len();
        if k == 0 {
            return vec![0; n];
        }
        let mut res = vec![];
        for i in 0..n {
            let mut sum = 0;
            for j in 0..k.abs() {
                let index = if k > 0 {
                    (n as i32 + (i as i32 + 1 + j)) as usize % n
                } else {
                    (n as i32 + (i as i32 - 1 - j)) as usize % n
                };
                sum += code[index];
            }
            res.push(sum);
        }
        res
    }
}
#[test]
fn test() {
    let code = vec![5, 7, 1, 4];
    let k = 3;
    let res = vec![12, 10, 16, 13];
    assert_eq!(Solution::decrypt(code, k), res);
    let code = vec![1, 2, 3, 4];
    let k = 0;
    let res = vec![0, 0, 0, 0];
    assert_eq!(Solution::decrypt(code, k), res);
    let code = vec![2, 4, 9, 3];
    let k = -2;
    let res = vec![12, 5, 6, 13];
    assert_eq!(Solution::decrypt(code, k), res);
}

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