1238. Circular Permutation in Binary Representation

Given 2 integers `n` and `start`. Your task is return any permutation `p` of `(0,1,2.....,2^n -1) `such that :

• `p[0] = start`
• `p[i]` and `p[i+1]` differ by only one bit in their binary representation.
• `p[0]` and `p[2^n -1]` must also differ by only one bit in their binary representation.

Example 1:

```Input: n = 2, start = 3
Output: [3,2,0,1]
Explanation: The binary representation of the permutation is (11,10,00,01).
All the adjacent element differ by one bit. Another valid permutation is [3,1,0,2]
```

Example 2:

```Input: n = 3, start = 2
Output: [2,6,7,5,4,0,1,3]
Explanation: The binary representation of the permutation is (010,110,111,101,100,000,001,011).
```

Constraints:

• `1 <= n <= 16`
• `0 <= start < 2 ^ n`

1238. Circular Permutation in Binary Representation
``````struct Solution;

impl Solution {
fn circular_permutation(n: i32, start: i32) -> Vec<i32> {
let mut res = vec![];
for i in 0..1 << n {
res.push(start ^ (i ^ i >> 1));
}
res
}
}

#[test]
fn test() {
let n = 2;
let start = 3;
let res = vec![3, 2, 0, 1];
assert_eq!(Solution::circular_permutation(n, start), res);
let n = 3;
let start = 2;
let res = vec![2, 3, 1, 0, 4, 5, 7, 6];
assert_eq!(Solution::circular_permutation(n, start), res);
}
``````