p0189_rotate_array.rs

// 189. Rotate Array
// Easy

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

// Example 1:

// Input: [1,2,3,4,5,6,7] and 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: [-1,-100,3,99] and 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]
// Note:

// 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?

pub struct Solution {}

impl Solution {
    pub fn rotate(nums: &mut Vec<i32>, k: i32) {
        let mut count = k % (nums.len() as i32);
        if count == 0 {
            return;
        }
        while count > 0 {
            let num = nums.pop().unwrap();
            nums.insert(0, num);
            count -= 1;
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn rotate_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]);
        nums = vec![-1, -100, 3, 99];
        Solution::rotate(&mut nums, 2);
        assert_eq!(nums, vec![3, 99, -1, -100]);
        nums = vec![-1, -100, 3, 99];
        Solution::rotate(&mut nums, 8);
        assert_eq!(nums, vec![-1, -100, 3, 99]);
    }
}