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.
代码：
class Solution {
public:
int bitwiseComplement(int N) {
if(N == 0) return 1;
vector<int> ans;
while(N) {
ans.push_back(!(N % 2));
N /= 2;
}
int sum = 0;
for(int i = 0; i < ans.size() / 2; i ++)
swap(ans[i], ans[ans.size() - i - 1]);
for(int i = 0; i < ans.size(); i ++)
sum += ans[i] * pow(2, ans.size() - 1 - i);
return sum;
}
int pow(int a, int b) {
int ans = 1;
while(b) {
if(b % 2) {
ans *= a;
b --;
} else {
a *= a;
b /= 2;
}
}
return ans;
}
};
周末开始啦