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.

题目分析

将整个数组向右移动k位，那么第i位的目标位置就是(i+k)%len

代码

class Solution {
public:
    void rotate(vector<int>& nums, int k) {
        vector<int> vec(nums);
        int len=nums.size();
        for(int i=0; i<len; i++) {
            nums[(i+k)%len] = vec[i];
        }
        return ;
    }
};

倒置的思路

将后k位倒置和前n-k位倒置，然后将整个数组倒置

class Solution 
    {
    public:
        void rotate(int nums[], int n, int k) 
        {
            k = k%n;
    
            // Reverse the first n - k numbers.
            // Index i (0 <= i < n - k) becomes n - k - i.
            reverse(nums, nums + n - k);
            
            // Reverse tha last k numbers.
            // Index n - k + i (0 <= i < k) becomes n - i.
            reverse(nums + n - k, nums + n);
            
            // Reverse all the numbers.
            // Index i (0 <= i < n - k) becomes n - (n - k - i) = i + k.
            // Index n - k + i (0 <= i < k) becomes n - (n - i) = i.
            reverse(nums, nums + n);
        }
    };