leetcode 1009. Complement of Base 10 Integer ( Python )

描述

Every non-negative integer N has a binary representation. For example, 5 can be represented as "101" in binary, 11 as "1011" in binary, and so on. Note that except for N = 0, there are no leading zeroes in any binary representation.

The complement of a binary representation is the number in binary you get when changing every 1 to a 0 and 0 to a 1. For example, the complement of "101" in binary is "010" in binary.

For a given number N in base-10, return the complement of it's binary representation as a base-10 integer.

Example 1:

Input: 5
Output: 2
Explanation: 5 is "101" in binary, with complement "010" in binary, which is 2 in base-10.
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Example 2:

Input: 7
Output: 0
Explanation: 7 is "111" in binary, with complement "000" in binary, which is 0 in base-10.
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Example 3:

Input: 10
Output: 5
Explanation: 10 is "1010" in binary, with complement "0101" in binary, which is 5 in base-10.
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Note:

0 <= N < 10^9
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解析

根據題意，就是把 N 變成二進制的形態，而後進行 0-1 變換，將變換後的數字再轉換回十進制。時間複雜度爲 O(N)，空間複雜度爲 O(N)，N 是二進制的位數。

解答

class Solution(object):
def bitwiseComplement(self, N):
    """
    :type N: int
    :rtype: int
    """
    result = ""
    nbins = bin(N)[2:]
    for i in nbins:
        result += str(int(i)^1)
    return int(result, 2)            
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運行結果

Runtime: 16 ms, faster than 77.81% of Python online submissions for Complement of Base 10 Integer.
Memory Usage: 11.7 MB, less than 79.49% of Python online submissions for Complement of Base 10 Integer.
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