# 1009. Complement of Base 10 Integer

## Description

The complement of an integer is the integer you get when you flip all the 0's to 1's and all the 1's to 0's in its binary representation.

• For example, The integer 5 is "101" in binary and its complement is "010" which is the integer 2.

Given an integer n, return its complement.

Example 1:

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


Example 2:

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


Example 3:

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


Constraints:

• 0 <= n < 109

Note: This question is the same as 476: https://leetcode.com/problems/number-complement/

## Solutions

• class Solution {
public int bitwiseComplement(int n) {
if (n == 0) {
return 1;
}
int ans = 0;
boolean find = false;
for (int i = 30; i >= 0; --i) {
int b = n & (1 << i);
if (!find && b == 0) {
continue;
}
find = true;
if (b == 0) {
ans |= (1 << i);
}
}
return ans;
}
}

• class Solution {
public:
int bitwiseComplement(int n) {
if (n == 0) return 1;
int ans = 0;
bool find = false;
for (int i = 30; i >= 0; --i) {
int b = n & (1 << i);
if (!find && b == 0) continue;
find = true;
if (b == 0) ans |= (1 << i);
}
return ans;
}
};

• class Solution:
def bitwiseComplement(self, n: int) -> int:
if n == 0:
return 1
ans = 0
find = False
for i in range(30, -1, -1):
b = n & (1 << i)
if not find and b == 0:
continue
find = True
if b == 0:
ans |= 1 << i
return ans


• func bitwiseComplement(n int) int {
if n == 0 {
return 1
}
ans := 0
find := false
for i := 30; i >= 0; i-- {
b := n & (1 << i)
if !find && b == 0 {
continue
}
find = true
if b == 0 {
ans |= (1 << i)
}
}
return ans
}