add complement of base 10 integer soln

0476_number-complement/README.md

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+The **complement** of an integer is the integer you get when you flip all the `0`'s to `1`'s and all the `1`'s to `0`'s in its binary representation.
+
+*   For example, The integer `5` is `"101"` in binary and its **complement** is `"010"` which is the integer `2`.
+
+Given an integer `num`, return _its complement_.
+
+**Example 1:**
+
+    Input: num = 5
+    Output: 2
+    Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.
+    
+
+**Example 2:**
+
+    Input: num = 1
+    Output: 0
+    Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.
+    
+
+**Constraints:**
+
+*   `1 <= num < 231`
+
+**Note:** This question is the same as 1009: [https://leetcode.com/problems/complement-of-base-10-integer/](https://leetcode.com/problems/complement-of-base-10-integer/)

0476_number-complement/python3/linear.py

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+# Time: O(N) where N is number of bits
+class Solution:
+    def findComplement(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

0476_number-complement/python3/solution.py

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+class Solution:
+    def findComplement(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

1054_complement-of-base-10-integer/README.md

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+The **complement** of an integer is the integer you get when you flip all the `0`'s to `1`'s and all the `1`'s to `0`'s in its binary representation.
+
+*   For example, The integer `5` is `"101"` in binary and its **complement** is `"010"` which is the integer `2`.
+
+Given an integer `n`, return _its complement_.
+
+**Example 1:**
+
+    Input: n = 5
+    Output: 2
+    Explanation: 5 is "101" in binary, with complement "010" in binary, which is 2 in base-10.
+    
+
+**Example 2:**
+
+    Input: n = 7
+    Output: 0
+    Explanation: 7 is "111" in binary, with complement "000" in binary, which is 0 in base-10.
+    
+
+**Example 3:**
+
+    Input: n = 10
+    Output: 5
+    Explanation: 10 is "1010" in binary, with complement "0101" in binary, which is 5 in base-10.
+    
+
+**Constraints:**
+
+*   `0 <= n < 109`
+
+**Note:** This question is the same as 476: [https://leetcode.com/problems/number-complement/](https://leetcode.com/problems/number-complement/)

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

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+# 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

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+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