feat(arrays, matrices): set matrix to zero

Author: BrianLusina

datastructures/arrays/matrix/settozero/README.md

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+# Set Matrix Zero
+
+Given a matrix, mat, if any element within the matrix is zero, set that row and column to zero. The performed operations 
+should be in place, i.e., the given matrix is modified directly without allocating another matrix.
+
+Constraints:
+
+Let `mat` be the matrix given as input to find the anagrams.
+
+- 1 <= `mat.row`, `mat.col` <= 20
+- -2^31 <= `mat[i][j]` <= 2^31-1
+
+## Examples
+
+![Example one](images/set_matrix_zero_example_one.png)
+![Example two](images/set_matrix_zero_example_two.png)
+![Example three](images/set_matrix_zero_example_three.png)

datastructures/arrays/matrix/settozero/__init__.py

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+from typing import List
+
+
+def set_matrix_zeros(mat: List[List[int]]) -> List[List[int]]:
+    """
+    Sets all elements in a matrix to zero if any row or column has at least one zero element.
+
+    ## Complexity Analysis
+
+    This solution is efficient in both time and space. The time complexity is O(rows × cols) because we scan through
+    the matrix a constant number of times. The space complexity is O(1) because we only use a couple of boolean
+    variables regardless of the matrix size, and we use the matrix itself for tracking.
+
+    Args:
+        mat (List): input matrix
+    Returns:
+        List[List[int]]modified matrix with all elements in any row or column containing a zero element set to zero
+    """
+    if not mat or not mat[0]:
+        return mat
+
+    row_length, col_length = len(mat), len(mat[0])
+
+    # Step 1: Check if the first row and first column originally contain zeros
+    # We need this info because we'll use them as markers
+    first_row_has_zero = any(mat[0][j] == 0 for j in range(col_length))
+    first_col_has_zero = any(mat[i][0] == 0 for i in range(row_length))
+
+    # Step 2: Use first row and column as markers for other rows/columns
+    # Scan the interior of the matrix (excluding first row and column)
+    for r in range(1, row_length):
+        for c in range(1, col_length):
+            if mat[r][c] == 0:
+                # Mark this row and column by setting the corresponding
+                # positions in the first row and column to zero
+                mat[r][0] = 0 # mark row as 0
+                mat[0][c] = 0 # mark column as 0
+
+    # Step 3: Use the markers to set zeros in the interior of the matrix
+    # We process from [1][1] onwards to avoid corrupting our markers
+    for r in range(1, row_length):
+        for c in range(1, col_length):
+            # If this row or column was marked, set this cell to zero
+            if mat[r][0] == 0 or mat[0][c] == 0:
+                mat[r][c] = 0
+
+    # Step 4: Finally, handle the first row and column based on our original checks
+    if first_row_has_zero:
+        for c in range(col_length):
+            mat[0][c] = 0
+    if first_col_has_zero:
+        for r in range(row_length):
+            mat[r][0] = 0
+
+    return mat

datastructures/arrays/matrix/settozero/images/set_matrix_zero_example_one.png

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+import unittest
+from . import set_matrix_zeros
+
+
+class SetMatrixZeroTestCase(unittest.TestCase):
+    def test_1(self):
+        matrix = [[1,2,3],[4,5,6],[7,0,9]]
+        expected = [[1,0,3],[4,0,6],[0,0,0]]
+        actual = set_matrix_zeros(matrix)
+        self.assertEqual(expected, actual)
+
+    def test_2(self):
+        matrix = [[1,2,3,4],[4,5,6,7],[8,9,4,6]]
+        expected = [[1,2,3,4],[4,5,6,7],[8,9,4,6]]
+        actual = set_matrix_zeros(matrix)
+        self.assertEqual(expected, actual)
+
+    def test_3(self):
+        matrix = [[1,1,0,1,1],[1,1,1,1,1],[1,1,1,1,1],[1,0,1,1,1],[1,1,1,1,1]]
+        expected = [[0, 0, 0, 0, 0], [1, 0, 0, 1, 1], [1, 0, 0, 1, 1], [0, 0, 0, 0, 0], [1, 0, 0, 1, 1]]
+        actual = set_matrix_zeros(matrix)
+        self.assertEqual(expected, actual)
+
+    def test_4(self):
+        matrix = [[1,1,1],[1,0,1],[1,1,1]]
+        expected = [[1, 0, 1], [0, 0, 0], [1, 0, 1]]
+        actual = set_matrix_zeros(matrix)
+        self.assertEqual(expected, actual)
+
+    def test_5(self):
+        matrix = [[3,5,2,0],[1,0,4,6],[7,3,2,4]]
+        expected = [[0, 0, 0, 0], [0, 0, 0, 0], [7, 0, 2, 0]]
+        actual = set_matrix_zeros(matrix)
+        self.assertEqual(expected, actual)
+
+
+if __name__ == '__main__':
+    unittest.main()