Algorithm to rotate an array in linear time

Question

How to rotate an integer array by i times using swap function only in linear time.

Answer 1

public int[] shift(int[] A, int K) {
    int N = A.length;
    if (N == 0)
        return A;
    int mid =  -K % N;
    if (mid < 0)
        mid += N;
    if (mid == 0)
        return A;

    reverseSubArray(A, 0 , mid - 1);

    reverseSubArray(A, mid , N - 1);

    reverseSubArray(A, 0 , N - 1);

    return A;
}

private void reverseSubArray(int[] A, int start , int end){
    int i = 0;
    int tmp;
    while (i < (end - start + 1) / 2) {
        tmp = A[i + start];
        A[i + start] = A[end - i];
        A[end - i] = tmp;
        i++;
    }

}

Doug McIlroy’s Handwaving Description