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Tail N Lines

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Problem statement

Implement the Unix tail -n command: given an array of strings representing the lines of a file and an integer n, return the last n lines.

If n is greater than or equal to the total number of lines, return all lines.

Follow-up: Optimize for memory and time complexity. A rolling window (circular buffer / deque of size n) achieves O(n) space and O(L) time where L is the total number of lines — avoiding storing the entire file.

Function

tail(lines: String[], n: int) → String[]

Examples

Example 1

lines = ["a","b","c","d","e"]n = 2return = ["d","e"]
The file has 5 lines. The last 2 lines are "d" and "e".

Example 2

lines = ["a","b","c"]n = 5return = ["a","b","c"]
n=5 exceeds the total number of lines (3), so all lines are returned.

More Confluent problems

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public String[] tail(String[] lines, int n) {
  // write your code here
}
lines["a","b","c","d","e"]
n2
expected["d", "e"]
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