Tenth Line - Practice Coding Problems

Tenth Line - Problem

Shell Easy

Your mission: Extract the 10th line from a text file named file.txt. Sounds simple? It is! But there are several elegant ways to accomplish this task using shell commands.

What you need to do:
• Read from a file called file.txt
• Print only the 10th line of that file
• Handle cases where the file might have fewer than 10 lines

Example:
If file.txt contains:

Line 1
Line 2
...
Line 10
Line 11

Your output should be: Line 10

Input & Output

basic_file.txt

$ Input: file.txt contains: Line 1 Line 2 Line 3 Line 4 Line 5 Line 6 Line 7 Line 8 Line 9 Line 10 Line 11 Line 12

› Output: Line 10

💡 Note: The file has more than 10 lines, so we successfully extract the 10th line

exactly_ten_lines.txt

$ Input: file.txt contains: First Second Third Fourth Fifth Sixth Seventh Eighth Ninth Tenth

› Output: Tenth

💡 Note: The file has exactly 10 lines, so the 10th line is the last line

fewer_lines.txt

$ Input: file.txt contains: Only line 1 Only line 2 Only line 3

› Output: (no output)

💡 Note: The file has fewer than 10 lines, so there's no 10th line to print

Visualization

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Understanding the Visualization

File Structure

Text file consists of sequentially numbered lines

Line Addressing

Different tools offer various ways to target specific lines

Extraction

Output only the content of the 10th line

Key Takeaway

🎯 Key Insight: While all approaches work, `sed -n '10p'` provides the most efficient solution with direct line addressing, avoiding unnecessary data processing and offering the cleanest syntax for this specific task.

Time & Space Complexity

Time Complexity

⏱️

O(n)

Reads lines sequentially until line 10, then exits

✓ Linear Growth

Space Complexity

O(1)

Constant space usage with early termination

✓ Linear Space

Constraints

The file is named file.txt
Each line contains at most 1000 characters
The file may have anywhere from 0 to 10⁶ lines
Handle gracefully when file has fewer than 10 lines

Asked in

G Google 12 a Amazon 8 f Meta 6 ⊞ Microsoft 5

The most efficient solution uses sed -n '10p' file.txt for direct line addressing. Alternative approaches include head -n 10 file.txt | tail -n 1 (readable pipeline) and awk 'NR==10 {print; exit}' file.txt (condition-based with early termination). All have O(n) time complexity but sed offers the most concise and efficient implementation.

Common Approaches

Approach	Time	Space	Notes
✓ AWK Pattern Matching	O(n)	O(1)	Use AWK's built-in line number variable NR to target line 10
SED Line Addressing (Optimal)	O(n)	O(1)	Use sed to directly address and print the 10th line
Head + Tail Combination	O(n)	O(1)	Use head to get first 10 lines, then tail to get the last one

AWK Pattern Matching — Algorithm Steps

AWK reads file line by line, maintaining NR (line number)
Check if NR == 10 using pattern matching
Print the line and exit to avoid processing remaining lines

Visualization

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Step-by-Step Walkthrough

NR Counter

AWK maintains automatic line number counter

Condition Check

For each line, check if NR == 10

Print & Exit

When condition met, print line and exit

Code -

solution.c — C

Time & Space Complexity

Time Complexity

⏱️

O(n)

Reads lines sequentially until line 10, then exits

✓ Linear Growth

Space Complexity

O(1)

Constant space usage with early termination

✓ Linear Space

Constraints

The file is named file.txt
Each line contains at most 1000 characters
The file may have anywhere from 0 to 10⁶ lines
Handle gracefully when file has fewer than 10 lines

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Smart Actions

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Input & Output

Visualization

Time & Space Complexity

Related Problems

Constraints

Common Approaches

AWK Pattern Matching — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Constraints

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