Rotate Array

Desicription

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

Example 1:

1
2
3
4
5
6
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:

1
2
3
4
5
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?

Solution

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
class Solution {
private:
    void fun(vector<int>& nums, int left, int right) {
        if(left >= right)
            return ;
        while(left <= right) {
            swap(nums[left], nums[right]);
            left++;
            right--;
        }
    }
public:
    void rotate(vector<int>& nums, int k) {
        k = k % nums.size();
        fun(nums, 0, nums.size() - 1);
        fun(nums, 0, k - 1);
        fun(nums, k, nums.size() - 1);
    }
};