Tenth Line

EASY

Description

Given a text file file.txt, print just the 10th line of the file.

Example:

Assume that file.txt has the following content:

Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10

Your script should output the tenth line, which is:

Line 10

Note:
1. If the file contains less than 10 lines, what should you output?
2. There's at least three different solutions. Try to explore all possibilities.

Approaches

Checkout 3 different approaches to solve Tenth Line. Click on different approaches to view the approach and algorithm in detail.

Iterative Reading with a Counter

A more memory-efficient approach is to read the file line by line, keeping track of the current line number. We stop reading and print the line as soon as we reach the 10th line.

Algorithm

Initialize a line counter to 0.
Open file.txt using a BufferedReader.
Read the file line by line in a loop.
For each line, increment the counter.
If the counter reaches 10, print the current line and exit the loop.
If the end of the file is reached before the counter hits 10, do nothing.

This method avoids loading the entire file into memory. Instead, it processes the file as a stream. We use a BufferedReader to read the file one line at a time. A counter variable is initialized to 1 and incremented for each line read. When the counter equals 10, we've found our target line. We print it and can immediately stop processing the rest of the file by breaking the loop. If the loop finishes (i.e., we reach the end of the file) and the counter is less than 10, it means the file has fewer than 10 lines, and nothing is printed.

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class IterativeRead {
    public static void main(String[] args) {
        String fileName = "file.txt";
        try (BufferedReader reader = new BufferedReader(new FileReader(fileName))) {
            String line;
            int lineCount = 0;
            while ((line = reader.readLine()) != null) {
                lineCount++;
                if (lineCount == 10) {
                    System.out.println(line);
                    break; // Stop reading after the 10th line
                }
            }
        } catch (IOException e) {
            System.err.println("Error reading file: " + e.getMessage());
        }
    }
}

Complexity Analysis

Time Complexity: O(L), where L is the number of characters up to the 10th line. In the worst case (file has fewer than 10 lines), it's O(N), where N is the total number of characters. For any file with at least 10 lines, this is constant time relative to the file size.Space Complexity: O(M), where M is the maximum length of a line in the file. This is because we only need to store one line at a time. It's often considered O(1) or constant space.

Pros and Cons

Pros:

Very memory efficient; suitable for files of any size.
Time efficient, as it stops reading as soon as the target line is found.

Cons:

Slightly more verbose than the first approach.
Does not provide random access to other lines without re-reading the file.

Video Solution

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