Sorting strings from the text file

Last Updated : 08 Apr, 2023

Given a text file "file.txt" that consists of strings, the task is to sort all the strings in alphabetical order in that text file.

Approach: The idea is to use the concept of File Handling and a text file(say file.txt) that contains all the strings. Below are the steps:

Create the file using fopen() and insert names into the file using fprintf().
Close the file using fclose().
Reopen the file for reading the names.
Read or scan the names from the file using fscanf() and store it in a vector of strings.
Sort the given string stored in the vector using the sort() function.
Now, insert the sorted string in that file and print it.

Below is the implementation of the above approach:

C++

// C++ program to sort given array
// of string stored in a file
#include <bits/stdc++.h>
#include <cstdlib>
#include <cstring>
#include <fstream>
using namespace std;

// Driver Code
int main()
{
    int N, i, j;

    // File pointer to open file
    FILE* f;

    // fopen() for creating of a file
    f = fopen("file.txt", "w");

    // Input number of strings
    // to be inserted in file
    cin >> n;

    vector<int> name(N);

    // Insert the strings into file
    for (i = 0; i < n; i++) {

        // Insert names in file
        cin >> name[i];

        // Writing into the file
        fprintf(f, "%s", name[i]);
    }

    // Close the file
    fclose(f);

    // Reopening in read mode
    f = fopen("file.txt", "r");

    // Check does file exist or not
    if (f == NULL) {
        cout << "File doesn't exist!";
        return 0;
    }

    // Read the file until it
    // encounters end of line
    while (!feof(f)) {
        fscanf(f, "%s", name[i]);
        i++;
    }
    n = i - 1;

    // Sort the strings
    sort(name.begin(), name.end());

    // Insert the strings into file
    // after sorting
    for (i = 0; i < n; i++) {

        // Write into the file
        fprintf(f, "%s", name[i]);
    }

    // Print the sorted names
    for (i = 0; i < n; i++) {
        cout << name[i] << '\n';
    }

    return 0;
}

Java

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class SortStringsFromFile {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // Input number of strings to be inserted in file
        System.out.print("Enter the number of strings: ");
        int n = scanner.nextInt();
        scanner.nextLine();

        try {
            // Open file for writing
            BufferedWriter writer = new BufferedWriter(new FileWriter("file.txt"));

            // Insert the strings into file
            for (int i = 0; i < n; i++) {
                System.out.print("Enter the string: ");
                String name = scanner.nextLine();

                // Writing into the file
                writer.write(name + "\n");
            }

            // Close the writer
            writer.close();

            // Open file for reading
            BufferedReader reader = new BufferedReader(new FileReader("file.txt"));

            // Read the lines until end of file is reached
            List<String> names = new ArrayList<String>();
            String line;
            while ((line = reader.readLine()) != null) {
                names.add(line);
            }

            // Close the reader
            reader.close();

            // Sort the strings
            Collections.sort(names);

            // Open the file for writing
            writer = new BufferedWriter(new FileWriter("file.txt"));

            // Insert the sorted strings into the file
            for (String name : names) {
                writer.write(name + "\n");
            }

            // Close the writer
            writer.close();

            // Print the sorted names
            for (String name : names) {
                System.out.println(name);
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

        scanner.close();
    }
}

Python3

# Python program to sort given array of string stored in a file

# Input number of strings to be inserted in file
N = int(input("Enter the number of strings: "))

# Open file for writing
with open("file.txt", "w") as f:
    # Insert the strings into file
    for i in range(N):
        name = input("Enter the string: ")
        # Writing into the file
        f.write(name + "\n")

# Open file for reading
with open("file.txt", "r") as f:
    # Read the lines until end of file is reached
    names = [line.strip() for line in f.readlines()]

# Sort the strings
names.sort()

# Open the file for writing
with open("file.txt", "w") as f:
    # Insert the sorted strings into the file
    for name in names:
        f.write(name + "\n")

# Print the sorted names
for name in names:
    print(name)

using System;
using System.Collections.Generic;
using System.IO;

public class SortStringsFromFile
{
    public static void Main()
    {
        // Input number of strings to be inserted in file
        Console.Write("Enter the number of strings: ");
        int n = Convert.ToInt32(Console.ReadLine());

        try
        {
            // Open file for writing
            StreamWriter writer = new StreamWriter("file.txt");

            // Insert the strings into file
            for (int i = 0; i < n; i++)
            {
                Console.Write("Enter the string: ");
                string name = Console.ReadLine();

                // Writing into the file
                writer.WriteLine(name);
            }

            // Close the writer
            writer.Close();

            // Open file for reading
            StreamReader reader = new StreamReader("file.txt");

            // Read the lines until end of file is reached
            List<string> names = new List<string>();
            string line;
            while ((line = reader.ReadLine()) != null)
            {
                names.Add(line);
            }

            // Close the reader
            reader.Close();

            // Sort the strings
            names.Sort();

            // Open the file for writing
            writer = new StreamWriter("file.txt");

            // Insert the sorted strings into the file
            foreach (string name in names)
            {
                writer.WriteLine(name);
            }

            // Close the writer
            writer.Close();

            // Print the sorted names
            foreach (string name in names)
            {
                Console.WriteLine(name);
            }

        }
        catch (IOException e)
        {
            Console.WriteLine("Error: " + e.Message);
        }

        Console.ReadLine();
    }
}

JavaScript

const readline = require('readline');
const fs = require('fs');

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

// Open file for writing
const f = fs.openSync('file.txt', 'w');

rl.question('Input number of strings to be inserted in file: ', (n) => {
  let names = [];
  
  // Insert the strings into file
  for (let i = 0; i < n; i++) {
    rl.question('Enter name: ', (name) => {
      names.push(name);
      // Writing into the file
      fs.writeSync(f, name);
      if (i !== n - 1) {
        fs.writeSync(f, '\n');
      } else {
        // Close the file
        fs.closeSync(f);

        // Reopening in read mode
        const data = fs.readFileSync('file.txt', 'utf8').split('\n');
        const len = data.length;
        if (data[len - 1] === '') {
          data.pop();
        }

        // Sort the strings
        data.sort();

        // Insert the strings into file after sorting
        fs.writeFileSync('file.txt', data.join('\n'));

        // Print the sorted names
        console.log(data.join('\n'));
      }
    });
  }
});