1009.Complement of Base 10 Integer¶
Tags: Easy Bit Manipulation
Links: https://leetcode.com/problems/complement-of-base-10-integer/
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.
Example 2:
Input: 7
Output: 0
Explanation: 7 is "111" in binary, with complement "000" in binary, which is 0 in base-10.
Example 3:
Input: 10
Output: 5
Explanation: 10 is "1010" in binary, with complement "0101" in binary, which is 5 in base-10.
Note:
0 <= N < 10^9- This question is the same as 476: https://leetcode.com/problems/number-complement/
class Solution {
public:
int bitwiseComplement(int N) {
std::ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
if (N == 0) return 1;
unsigned int mask = INT_MAX;
while (mask & N) mask <<= 1;
return (~N) & (~mask);
}
};
按位取反很自然的联想到运算符~，但是如果能够固定数量的按位取反，其实可以考虑利用INT_MAX的移位操作，不断左移，直到和num的与运算为0，那么就可以确定需要按位取反的有多少位了，注意存在输入为0的情形。另外要用unsigned int类型。