Cloudera

2020-10-05

## 1009. Complement of Base 10 Integer

### Question:

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:

1. `0 <= N < 10^9`
2. This question is the same as 476: LeetCode Question 476

### Solution:

Using XOR(^) to compare each digit with 1.

``````class Solution {
public int bitwiseComplement(int N) {
if (N == 0) return 1;
if (N == 1) return 0;
int orBit = 1;
int rest = N;
while (rest != 0) {
N ^= orBit;
orBit <<= 1;
rest >>= 1;
}
return N;
}
}
``````

Using XOR(^) to compare with the largest value with current number of digits. It may have the integer overflow problem.

``````class Solution {
public int bitwiseComplement(int N) {
if (N == 0) return 1;
if (N == 1) return 0;
int orBit = 1;
while (orBit <= N) {
orBit <<= 1;
}
return N ^ (orBit - 1);
}
}
``````