add complement of base 10 integer soln

1054_complement-of-base-10-integer/python3/linear.py

@@ -0,0 +1,18 @@
+# Time: O(N) where N is number of bits
+class Solution:
+    def bitwiseComplement(self, n: int) -> int:
+        if n == 0:
+            return 1
+        
+        cn, bit = n, 1
+        
+        while n > 0:
+            # XOR 1 can be used to flip bit.
+            # 0 XOR 1 = 1
+            # 1 XOR 1 = 0
+            cn = cn ^ bit
+            
+            bit = bit << 1
+            n = n >> 1
+        
+        return cn

1054_complement-of-base-10-integer/python3/solution.py

@@ -0,0 +1,17 @@
+class Solution:
+    def bitwiseComplement(self, n: int) -> int:
+        if n == 0:
+            return 1
+
+        mask = n
+        
+        # Create mask of length matching num of bits
+        # in n (taken from Hacker's Delight, Figure 3-1)
+        mask |= mask >> 1    # \
+        mask |= mask >> 2    #  \
+        mask |= mask >> 4    #   |> Totalling 31 bits
+        mask |= mask >> 8    #  /
+        mask |= mask >> 16   # /
+        
+        # XOR 1 will flip the bit
+        return n ^ mask