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This approach uses a sliding window technique to efficiently calculate the sum of required elements. By maintaining a running sum for the window and updating it as you slide, you can achieve the necessary transformation in linear time. The key is to account for the circular nature of the array using modulo operations to wrap around indices.
Time Complexity: O(n), where n is the length of the `code` array. Each element is processed once with constant-time window updates.
Space Complexity: O(1) auxiliary space (excluding the output array).
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The Java solution carries on with a two-pointer approach to maintain a constant-time cumulative sum, updating as the window traverses the code array by adjusting indices with modulo operations. This facilitates handling of circular formats smoothly.
This approach is straightforward but less efficient, involving a direct sum computation for each index by wrapping around using the modulo operator. Each element's circular context is individually recalculated, following conditions for the sign of k.
Time Complexity: O(n*k) with n as length of `code` and k an absolute value.
Space Complexity: O(1) extra space beyond output.
1#include <stdio.h>
2#include <stdlib.h>
3
4int* decrypt(int* code, int codeSize, int k, int* returnSize) {
5 *returnSize = codeSize;
6 int* result = (int*)malloc(sizeof(int) * codeSize);
7
8 if (k == 0) {
9 for (int i = 0; i < codeSize; i++) {
10 result[i] = 0;
11 }
12 } else {
13 for (int i = 0; i < codeSize; i++) {
14 int sum = 0;
15 for (int j = 1; j <= abs(k); j++) {
16 int index = (k > 0) ? (i + j) % codeSize : (i - j + codeSize) % codeSize;
17 sum += code[index];
18 }
19 result[i] = sum;
20 }
21 }
22 return result;
23}
24
25int main() {
26 int code[] = {5, 7, 1, 4};
27 int k = 3;
28 int returnSize;
29 int* decrypted = decrypt(code, 4, k, &returnSize);
30 for (int i = 0; i < returnSize; i++) {
31 printf("%d ", decrypted[i]);
32 }
33 free(decrypted);
34 return 0;
35}
36The C implementation iterates over each element in the code for every ith position, calculating indices either forward or backward with the consideration of code's circular nature via modulus operation. Simple yet clear, this needs careful attention to negative index wrapping.