题目

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:

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

Example 2:

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

Example 3:

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

Note:

  1. 0 <= N < 10^9
  2. This question is the same as 476: https://leetcode.com/problems/number-complement/

题意

求一个整数二进制位全部取反后得到的十进制数。

思路

直接照做即可。

代码实现

Java

  1. class Solution {
  2.     public int bitwiseComplement(int N) {
  3.         if (N == 0) {
  4.             return 1;
  5.         }
  7.         int ans = 0;
  8.         int base = 1;
  9.         while (N != 0) {
  10.             ans += base * ((N % 2 + 1) % 2);
  11.             base *= 2;
  12.             N = N / 2;
  13.         }
  14.         return ans;
  15.     }
  16. }