FastPrep
Problem

Update Logs by Symmetric XOR

Learn this problem
Salesforce logoSalesforceFULLTIMEOA
See Salesforce hiring insights

Problem statement

You are given an integer array log of size n and a non-negative integer iterations.

The updates are applied sequentially and in-place. For each iteration i from 0 to iterations - 1:

  1. Compute index = i mod n.
  2. Compute symmetric = n - index - 1.
  3. Set log[index] = log[index] XOR log[symmetric], using the current array values at that moment.

If index == symmetric, the element is updated to 0 because x XOR x = 0. Return the final array after all iterations are complete. Since iterations can be very large, solutions should reason about the repeated index cycle instead of simulating every iteration one by one.

Function

updateLogsBySymmetricXor(log: int[], iterations: long) → int[]

Examples

Example 1

log = [1, 2, 3]iterations = 2return = [2, 0, 3]

Iteration 0 updates index 0: 1 XOR 3 = 2, so the array becomes [2,2,3]. Iteration 1 updates the middle index, where index == symmetric, so 2 XOR 2 = 0. The result is [2,0,3].

Example 2

log = [4, 7, 1, 2]iterations = 5return = [2, 6, 7, 4]

The updates are in-place at indices 0,1,2,3,0. The array changes as [4,7,1,2] -> [6,7,1,2] -> [6,6,1,2] -> [6,6,7,2] -> [6,6,7,4] -> [2,6,7,4].

Constraints

  • 1 <= log.length <= 2 * 10^5
  • 0 <= log[i] <= 10^9
  • 0 <= iterations <= 10^18

More Salesforce problems

drafts saved locally
public int[] updateLogsBySymmetricXor(int[] log, long iterations) {
  // write your code here
}
log[1, 2, 3]
iterations2
expected[2, 0, 3]
checking account