189. Rotate Array

Given an array, rotate the array to the right by k steps, where k is non-negative.

Follow up:

  • Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
  • Could you do it in-place with O(1) extra space?

 

Example 1:

Input: nums = [1,2,3,4,5,6,7], k = 3
Output: [5,6,7,1,2,3,4]
Explanation:
rotate 1 steps to the right: [7,1,2,3,4,5,6]
rotate 2 steps to the right: [6,7,1,2,3,4,5]
rotate 3 steps to the right: [5,6,7,1,2,3,4]

Example 2:

Input: nums = [-1,-100,3,99], k = 2
Output: [3,99,-1,-100]
Explanation: 
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]

 

Constraints:

  • 1 <= nums.length <= 2 * 104
  • -231 <= nums[i] <= 231 - 1
  • 0 <= k <= 105

Rust Solution

struct Solution;

impl Solution {
    fn rotate(nums: &mut Vec<i32>, k: i32) {
        let k = k as usize % nums.len();
        nums[..].reverse();
        nums[0..k].reverse();
        nums[k..].reverse();
        //      nums.rotate_right(k);
    }
}

#[test]
fn test() {
    let mut nums = vec![1, 2, 3, 4, 5, 6, 7];
    Solution::rotate(&mut nums, 3);
    assert_eq!(nums, vec![5, 6, 7, 1, 2, 3, 4]);
}

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