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].

Solution1

class Solution {
public:
    void rotate(vector<int>& nums, int k) {
        int n = nums.size();
        if ( n == 0 ) return;
        k = k%n;
        reverse(nums.begin(), nums.begin() + n-k);
        reverse(nums.begin() + n-k, nums.end());
        reverse(nums.begin(), nums.end());
        return;
    }
};

Solution2

class Solution {
public:
    int common(int n, int k) {
        int i1 = max(n, k), i2 = min(n, k);
        if ( i1%i2 == 0 ) return i2;
        return ( common(i1-i2, i2) );
    }
    void rotate(vector<int>& nums, int k) {
        int n = nums.size();
        if ( n <= 1 or k%n == 0 ) return;
        k = k%n;
        int n0 = common(n, k);
        for ( int i = 0; i <= n0-1; i++) {
            int i0 = i, ilast = nums[i0], j = (i0+k)%n;
            while ( j != i0 ) {
                int tmp = nums[j];
                nums[j] = ilast;
                ilast = tmp;
                j = (j+k)%n;
            }
            nums[i0] = ilast;
        }
        return;
    }
};