|
| 1 | +""" |
| 2 | +Author : Abhiraj Mandal |
| 3 | +Date : October 3, 2025 |
| 4 | +
|
| 5 | +This is a pure Python implementation to calculate the cumulative XOR of all |
| 6 | +sliding windows of size k in an array generated via a linear recurrence. |
| 7 | +
|
| 8 | +The problem is : |
| 9 | +Given parameters n, k, x, multiplier, increment, modulo, generate an array: |
| 10 | + arr[0] = x |
| 11 | + arr[i] = (multiplier * arr[i-1] + increment) % modulo |
| 12 | +Compute the XOR of each window of size k, and cumulatively XOR all windows. |
| 13 | +""" |
| 14 | + |
| 15 | + |
| 16 | +class SlidingWindowXOR: |
| 17 | + """ |
| 18 | + Use: |
| 19 | + solver = SlidingWindowXOR() |
| 20 | + result = solver.compute(n, k, x, multiplier, increment, modulo) |
| 21 | + """ |
| 22 | + |
| 23 | + def compute(self, n: int, k: int, x: int, multiplier: int, |
| 24 | + increment: int, modulo: int) -> int: |
| 25 | + """ |
| 26 | + Compute cumulative XOR of all sliding windows of size k. |
| 27 | +
|
| 28 | + >>> SlidingWindowXOR().compute(5, 2, 1, 1, 1, 100) |
| 29 | + 0 |
| 30 | + >>> SlidingWindowXOR().compute(2, 1, 2, 3, 4, 5) |
| 31 | + 2 |
| 32 | + """ |
| 33 | + # Generate the array using recurrence |
| 34 | + arr = [0] * n |
| 35 | + arr[0] = x |
| 36 | + for i in range(1, n): |
| 37 | + arr[i] = (multiplier * arr[i - 1] + increment) % modulo |
| 38 | + |
| 39 | + x1 = 0 # XOR of current window |
| 40 | + x2 = 0 # cumulative XOR of all windows |
| 41 | + left = 0 |
| 42 | + |
| 43 | + for right in range(n): |
| 44 | + x1 ^= arr[right] # include current element |
| 45 | + if right - left + 1 > k: |
| 46 | + x1 ^= arr[left] # remove leftmost element |
| 47 | + left += 1 |
| 48 | + if right - left + 1 == k: |
| 49 | + x2 ^= x1 |
| 50 | + |
| 51 | + return x2 |
| 52 | + |
| 53 | + |
| 54 | +if __name__ == "__main__": |
| 55 | + solver = SlidingWindowXOR() |
| 56 | + |
| 57 | + print("************ Testing Sliding Window XOR Algorithm ************\n") |
| 58 | + |
| 59 | + # Example testcases |
| 60 | + test_cases = [ |
| 61 | + (100, 20, 3, 7, 1, 997, 1019), |
| 62 | + (2, 1, 2, 3, 4, 5, 2), |
| 63 | + (5, 2, 1, 1, 1, 100, 4), |
| 64 | + (3, 5, 5, 2, 1, 100, 0), |
| 65 | + (4, 4, 3, 1, 0, 10, 0) |
| 66 | + ] |
| 67 | + |
| 68 | + for idx, (n, k, x, m, inc, mod, expected) in enumerate(test_cases, 1): |
| 69 | + result = solver.compute(n, k, x, m, inc, mod) |
| 70 | + print(f"Testcase {idx}: Expected={expected}, Got={result}") |
| 71 | + assert result == expected, f"Testcase {idx} failed!" |
| 72 | + |
| 73 | + print("\nAll test cases successfully passed!") |
| 74 | + print("********** End of Testing Sliding Window XOR Algorithm **********") |
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