Rotate Array

Reverse three segments\n\nFor a right rotation, first handle an empty array, then set k %= n; rotating by a full array length changes nothing. Reverse the entire array, reverse indices 0..k-1, and reverse k..n-1. For example, [1,2,3,4,5,6,7] with k = 3 becomes [7,6,5,4,3,2,1], then [5,6,7,4,3,2,1], then [5,6,7,1,2,3,4]. The first reversal brings the desired suffix to the front but reverses both pieces; the two smaller reversals restore their internal order. Each reversal is linear over disjoint or bounded segments, so total time is O(n) and extra space is O(1). Test k = 0, k > n, n = 1, duplicate values, and an empty input before taking modulo. If a non-mutating result is required, say so and use an output array instead.