189. Rotate Array

Rotate an array of n elements to the right by k steps.

For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].

Note:
Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.

[show hint]

Related problem: Reverse Words in a String II

Credits:
Special thanks to @Freezen for adding this problem and creating all test cases.

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Solution:

Tips:

reverse whole array, then partially reverse every part. K needs to be specially tackled, if k greater than the length of array. k %= array.length.

Java Code:

public class Solution {
    public void rotate(int[] nums, int k) {
        if (k == 0) {
            return;
        }
        
        k %= nums.length;
        int left = 0;
        int right = nums.length - 1;
        // reverse for whole array
        for (; left < right; left++) {
            int t = nums[left];
            nums[left] = nums[right];
            nums[right] = t;
            right --;
        }
        
        // partial reverse for the previous part
        left = 0;
        right = k - 1;
        for (; left < right; left++) {
            int t = nums[left];
            nums[left] = nums[right];
            nums[right] = t;
            right --;
        }
        // partial reverse for the next part
        left = k;
        right = nums.length - 1;
        for (; left < right; left++) {
            int t = nums[left];
            nums[left] = nums[right];
            nums[right] = t;
            right --;
        }
    }
}