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+"""
+73. Set Matrix Zeroes
+Difficulty: Medium
+https://leetcode.com/problems/set-matrix-zeroes/
+
+──────────────────────────────────────────────────
+
+Given an m x n integer matrix matrix, if an element is 0, set its
+entire row and column to 0's.
+
+You must do it in place.
+
+
+
+Example 1:
+
+Input: matrix = [[1,1,1],[1,0,1],[1,1,1]]
+Output: [[1,0,1],[0,0,0],[1,0,1]]
+
+Example 2:
+
+Input: matrix = [[0,1,2,0],[3,4,5,2],[1,3,1,5]]
+Output: [[0,0,0,0],[0,4,5,0],[0,3,1,0]]
+
+
+
+Constraints:
+
+        • m == matrix.length
+
+        • n == matrix[0].length
+
+        • 1 <= m, n <= 200
+
+        • -2^31 <= matrix[i][j] <= 2^31 - 1
+
+
+
+Follow up:
+
+• A straightforward solution using O(mn) space is probably a bad
+idea.
+
+• A simple improvement uses O(m + n) space, but still not the best
+solution.
+
+        • Could you devise a constant space solution?
+"""
+
+
+class Solution:
+    def setZeroes(self, matrix: List[List[int]]) -> None:
+        """
+        Do not return anything, modify matrix in-place instead.
+        """
+        m, n = len(matrix), len(matrix[0])
+
+        # 1. remember if row 0 or column 0 have their own zeros
+        row0_zero = any(matrix[0][c] == 0 for c in range(n))
+        col0_zero = any(matrix[r][0] == 0 for r in range(m))
+
+        # 2. use row 0 and column 0 as marker lists
+        for r in range(1, m):
+            for c in range(1, n):
+                if matrix[r][c] == 0:
+                    matrix[r][0] = 0
+                    matrix[0][c] = 0
+
+        # 3. zero the inner cells from the markers
+        for r in range(1, m):
+            for c in range(1, n):
+                if matrix[r][0] == 0 or matrix[0][c] == 0:
+                    matrix[r][c] = 0
+
+        # 4. handle row 0 and column 0 last
+        if row0_zero:
+            for c in range(n):
+                matrix[0][c] = 0
+        if col0_zero:
+            for r in range(m):
+                matrix[r][0] = 0