# 1652. Defuse the Bomb

## 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

• class Solution {
public int[] decrypt(int[] code, int k) {
int n = code.length;
int[] ans = new int[n];
if (k == 0) {
return ans;
}
for (int i = 0; i < n; ++i) {
if (k > 0) {
for (int j = i + 1; j < i + k + 1; ++j) {
ans[i] += code[j % n];
}
} else {
for (int j = i + k; j < i; ++j) {
ans[i] += code[(j + n) % n];
}
}
}
return ans;
}
}

• class Solution {
public:
vector<int> decrypt(vector<int>& code, int k) {
int n = code.size();
vector<int> ans(n);
if (k == 0) {
return ans;
}
for (int i = 0; i < n; ++i) {
if (k > 0) {
for (int j = i + 1; j < i + k + 1; ++j) {
ans[i] += code[j % n];
}
} else {
for (int j = i + k; j < i; ++j) {
ans[i] += code[(j + n) % n];
}
}
}
return ans;
}
};

• class Solution:
def decrypt(self, code: List[int], k: int) -> List[int]:
n = len(code)
ans = [0] * n
if k == 0:
return ans
for i in range(n):
if k > 0:
for j in range(i + 1, i + k + 1):
ans[i] += code[j % n]
else:
for j in range(i + k, i):
ans[i] += code[(j + n) % n]
return ans


• func decrypt(code []int, k int) []int {
n := len(code)
ans := make([]int, n)
if k == 0 {
return ans
}
for i := 0; i < n; i++ {
if k > 0 {
for j := i + 1; j < i+k+1; j++ {
ans[i] += code[j%n]
}
} else {
for j := i + k; j < i; j++ {
ans[i] += code[(j+n)%n]
}
}
}
return ans
}

• function decrypt(code: number[], k: number): number[] {
const n = code.length;
if (k === 0) {
return code.fill(0);
}
const isPrefix = k < 0;
if (isPrefix) {
k *= -1;
}
const map = new Map<number, [number, number]>();
let prefix = 0;
let suffix = 0;
for (let i = 1; i <= k; i++) {
prefix += code[n - i];
suffix += code[i];
}
map.set(0, [prefix, suffix]);

for (let i = 1; i < n; i++) {
let [p, s] = map.get(i - 1);
p -= code[n - k - 1 + i] ?? code[i - k - 1];
p += code[i - 1];
s -= code[i];
s += code[i + k] ?? code[i + k - n];
map.set(i, [p, s]);
}
for (let i = 0; i < n; i++) {
code[i] = map.get(i)[Number(!isPrefix)];
}
return code;
}