476. Number Complement

476. Number Complement

Easy

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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: Loading...

class Solution:
    def findComplement(self, num: int) -> int:
        """
        assert Solution().findComplement(5) == 2
        assert Solution().findComplement(1) == 0
        assert Solution().findComplement(8) == 7
        assert Solution().findComplement(13) == 2

        解题思路：将num不断向右移位取末位数，若末位数位0，将1向左移循环次数位添加到结果数里
        时间复杂度：O(logn)
        """
        sign, result = 0, 0
        while num != 0:
            if num & 1 == 0:
                result += 1 << sign
            num >>= 1
            sign += 1
        return result