What is the order of these elements after second pass of the merge sort…

Bottom-up merge sort treats every element as a sorted run of length 1, then repeatedly merges adjacent runs in pairs, doubling the run length each pass — pass 1 produces runs of size 2, pass 2 merges those into runs of size 4, pass 3 into runs of size 8, and so on. Any run left without a neighbour at the end of a pass simply carries forward unchanged into the next pass.

1. Start with the array as nine separate runs of size 1: 200 | 470 | 150 | 80 | 90 | 300 | 400 | 70 | 120.

2. Pass 1 merges adjacent runs in pairs: (200, 470) stays 200, 470; (150, 80) becomes 80, 150; (90, 300) stays 90, 300; (400, 70) becomes 70, 400; the run (120) has no partner and carries forward alone.

3. After pass 1 the array reads: 200, 470, 80, 150, 90, 300, 70, 400, 120 — four runs of size 2 and one leftover run of size 1.

4. Pass 2 merges those adjacent runs of size 2 in pairs: merging (200, 470) with (80, 150) gives 80, 150, 200, 470; merging (90, 300) with (70, 400) gives 70, 90, 300, 400; the leftover run (120) still has no partner, so it carries forward unchanged.

5. After pass 2 the array reads: 80, 150, 200, 470, 70, 90, 300, 400, 120.

Checking the result: all nine original values (200, 470, 150, 80, 90, 300, 400, 70, 120) appear exactly once, and each merged run of four is strictly increasing — 80 < 150 < 200 < 470 and 70 < 90 < 300 < 400 — confirming both merges were carried out correctly.

So the order of the elements after the second pass is: 80, 150, 200, 470, 70, 90, 300, 400, 120.