Python Coding Challenge - Question with Answer (ID -200126)

 

🔹Step 1 — Understand range(len(arr))

len(arr) = 4, so:

range(4) → 0, 1, 2, 3

So the loop runs 4 times with i = 0, 1, 2, 3.

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🔹 Step 2 — Understand negative indexing

In Python:

Index	0	1	2	3
Value	1	2	3	4
Negative index	-4	-3	-2	-1

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🔹 Step 3 — Iterate and modify the list

Iteration 1: i = 0

arr[0] = arr[-0]

But -0 == 0, so:

arr[0] = arr[0] = 1

Array remains:
👉 [1, 2, 3, 4]

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Iteration 2: i = 1

arr[1] = arr[-1] 

arr[-1] = 4

So:

arr[1] = 4

Array becomes:
👉 [1, 4, 3, 4]

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Iteration 3: i = 2

arr[2] = arr[-2] 

arr[-2] = 3

So:

arr[2] = 3

Array becomes:
👉 [1, 4, 3, 4] (no change here)

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Iteration 4: i = 3

arr[3] = arr[-3]

arr[-3] = 4 (because arr is now [1,4,3,4])

So:

arr[3] = 4

Final array:
👉 [1, 4, 3, 4]

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✅ Final Output

[1, 4, 3, 4]

Mastering Pandas with Python