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You are given a 1D array original and two integers, m and n, which represent the dimensions of a 2D array. You need to transform the 1D array into a 2D array with m rows and n columns. If it is not possible to meet the desired dimensions, return an empty 2D array.

Clarifying Questions

1. What should be the output if the conversion is not possible?
   • If the conversion is not possible, return an empty 2D array.
2. Will the input always be a valid 1D array?
   • Yes, you can assume that the input is always a valid 1D array.
3. Can m or n be zero or negative?
   • No, m and n will always be positive integers.

Strategy

1. Check if Conversion is Possible:
   • The conversion is possible if the length of the original array equals m * n.
   • If not, return an empty list.
2. Reshape the Array:
   • Iterate over the elements of original and fill a 2D array row by row.

Code

def construct2DArray(original, m, n):
    # Check if conversion is possible
    if len(original) != m * n:
        return []

    # Initialize the 2D array
    result = []
    for i in range(m):
        # Create a row and insert the correct elements
        row = original[i * n:(i + 1) * n]
        result.append(row)

    return result

# Example usage:
original = [1, 2, 3, 4]
m = 2
n = 2
print(construct2DArray(original, m, n))  # Output: [[1, 2], [3, 4]]

Time Complexity

• Time Complexity: O(m * n) or equivalently O(len(original))
  • We iterate through the list exactly once to create the 2D array.
• Space Complexity: O(m * n)
  • We use extra space to store the resultant 2D array.

Feel free to ask if you have any further questions or need additional clarifications!

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