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

Rust Solution

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);
}

Having problems with this solution? Click here to submit an issue on github.