[leetcode] Rotate Array


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]

Hint:
Could you do it in-place with O(1) extra space?

Related problem: Reverse Words in a String II

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

Easy question, but ask the interviewer what we should do if k is bigger than nums.size()

//What if k is bigger than n?
class Solution {
public:
    void rotate(vector<int>& nums, int k) {
        //extreme case
        if(nums.size() == 0 || k == 0) return ;
        k = k % nums.size();//k may be 0
        for(int i = 0; i < k; i++){
            nums.insert(nums.begin(), nums.back());
            nums.pop_back();
        }
    }
};

Another approach

class Solution {
public:
    void rotate(vector<int>& nums, int k) {
        if(k == 0 || nums.size() == 0)
            return;
        k %= nums.size();
        int len = nums.size();
        vector<int> ans;
        ans = vector<int>(nums.end() - k, nums.end());
        for(size_t i = 0; i < len - k; i++){
            ans.push_back(nums[i]);
        }
        nums = ans;
    }
};

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