Minimum Operations to Make a Uni-Value Grid LeetCode solution in Python

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class Solution:
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    def minOperations(self, grid: List[List[int]], x: int) -> int:
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        m = len(grid)
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        n = len(grid[0])
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        # handle the edge case
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        if m == 1 and n == 1:
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            return 0
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        # transform grid to array, easier to operate
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        arr = []
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        for i in range(m):
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            arr += grid[i]
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        arr.sort()
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        # the median is arr[len(arr)//2] when len(arr) is odd
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        # or may be arr[len(arr)//2] and arr[len(arr)//2-1] when len(arr) is even.
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        cand1 = arr[len(arr) // 2]
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        cand2 = arr[len(arr) // 2 - 1]
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        return min(
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            self.get_num_operations_to_target(grid, cand1, x),
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            self.get_num_operations_to_target(grid, cand2, x),
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        )
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    def get_num_operations_to_target(self, grid, target, x):
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        """Get the total number of operations to transform all grid elements to the target value."""
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        ans = 0
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        for i in range(len(grid)):
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            for j in range(len(grid[0])):
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                if abs(grid[i][j] - target) % x != 0:
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                    return -1
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                else:
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                    ans += abs(grid[i][j] - target) // x
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        return ans