set matrix zeroes

Author: jungsiroo

set-matrix-zeroes/jungsiroo.py

@@ -0,0 +1,43 @@
+class Solution:
+    def setZeroes(self, matrix: List[List[int]]) -> None:
+        """
+        Do not return anything, modify matrix in-place instead.
+        """
+
+        """
+        # Naive change : save rows and cols
+        # SC : O(m+n)
+        row_zero, col_zero = set(), set()
+        
+        rows, cols = len(matrix), len(matrix[0])
+        for i in range(rows):
+            for j in range(cols):
+                if matrix[i][j] == 0:
+                    row_zero.add(i)
+                    col_zero.add(j)
+        
+        for i in range(rows):
+            for j in range(cols):
+                if i in row_zero or j in col_zero:
+                    matrix[i][j] = 0
+        """
+
+        # Constant Space Complexity using bitmasking
+		# 0인 구간을 toggle 시켜놓고 확인하는 방법
+        def is_on(number, k):
+            return (number & (1<<k)) != 0
+        
+        row_zero, col_zero = 0, 0
+        
+        rows, cols = len(matrix), len(matrix[0])
+        for i in range(rows):
+            for j in range(cols):
+                if matrix[i][j] == 0:
+                    row_zero |= (1 << i)
+                    col_zero |= (1 << j)
+        
+        for i in range(rows):
+            for j in range(cols):
+                if is_on(row_zero, i) or is_on(col_zero, j):
+                    matrix[i][j] = 0
+