For this task, we use the Reversal Algorithm, the main logic behind this algorithm is to reverse the array in parts to get the desired output.
Input arr[ ] = [1, 2, 3, 4, 5, 6, 7], d = 2, n =7 A[ ] and B[ ] are parts of the array arr[ ] where
1) A[ ] has elements in the index range 0 to d A[ ] = [1, 2]
2) B[ ] has elements in the index range d to n B[ ] = [3, 4, 5, 6, 7]
3) Reverse array A[ ] Ar[ ] = [2, 1] then array ArB=[2, 1, 3, 4, 5, 6, 7]
4) Reverse array B[ ] Br[ ] = [7, 6, 5, 4, 3] then array ArBr = [2, 1, 7, 6, 5, 4, 3]
5) Reverse array ArBr[ ] (ArBr)r[ ] = [3, 4, 5, 6, 7, 1, 2]
6) arr[ ] = [3, 4, 5, 6, 7, 1, 2]