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authorJack Sangdahl <[email protected]>2024-07-02 11:21:43 -0600
committerJack Sangdahl <[email protected]>2024-07-02 11:21:43 -0600
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parent1cb433cf3ef98dc8fbd7722a05c09668199d3c26 (diff)
downloadleetcode-723e7b2800616a3d0aca5b8d5deb6e0b59606a3c.tar.gz
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1787. make the xor of all segments equal to zero
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+# 1787. Make the XOR of All Segments Equal to Zero
+import collections
+
+"""
+given an array 'nums' and an integer 'k'. the xor of a segment '[left,
+right]' where 'left <= right' is the xor of all the elements with indices
+between 'left' and 'right', inclusive 'nums[left] xor nums[left + 1] xor ...
+xor nums[right]'. return the minimum number of elements to change in the
+array such that the 'xor' of all segments of size 'k' is equal to zero
+"""
+
+
+class Solution(object):
+ def minChanges(self, nums, k):
+ """
+ :type nums: List[int]
+ :type k: int
+ :rtype: int
+ """
+ m = 1 << 10
+ freq = collections.defaultdict(collections.Counter)
+ for i, n in enumerate(nums):
+ freq[i % k][n] += 1
+ dp = [[0] * m for _ in range(k + 1)]
+ for i in range(1, m):
+ dp[0][i] = -float("inf")
+ for i in range(1, k + 1):
+ max_row = max(dp[i - 1])
+ for j in range(m):
+ for mask in freq[i - 1]:
+ dp[i][j] = max(
+ dp[i][j], max_row, dp[i - 1][j ^ mask] + freq[i - 1][mask]
+ )
+ return len(nums) - dp[-1][0]
+
+
+if __name__ == "__main__":
+ obj = Solution()
+ print(obj.minChanges(nums=[1, 2, 0, 3, 0], k=1))
+ print(obj.minChanges(nums=[3, 4, 5, 2, 1, 7, 3, 4, 7], k=3))
+ print(obj.minChanges(nums=[1, 2, 4, 1, 2, 5, 1, 2, 6], k=3))