First and last character of each word in a String

Given a string s consisting of multiple words, print the first and last character of each word. If a word contains only one character, print it twice (since the first and last characters are the same).
Note: The string will not contain leading or trailing spaces.

Examples:

Input: s = "Geeks for geeks"
Output: Gs fr gs
Explanation: "Geeks" → "Gs", "for" → "fr", "geeks" → "gs"
Input: s = "Computer applications"
Output: Cr as
Explanation: "Computer" → "Cr", "applications" → "as"
Input: s="Code a Program"
Output: Ce aa Pm
Explanation: "Code" → "Ce", "a" → "aa", "Program" → "Pm"

Table of Content

[Approach 1] String Traversal - O(n) time and O(1) space
[Approach 2] Using Stream Based Functions - O(n) time and O(1) space

[Approach 1] String Traversal - O(n) time and O(1) space

Run a loop from the first letter to the last letter.
Print the first and last letter of the string.
If there is a space in the string then print the character that lies just before space and just after space.

C++

#include <iostream>
using namespace std;

void FirstAndLast(string s)
{

    for (int i = 0; i < s.length(); i++)
    {
        // If it is the first word
        // of the string then print it.
        if (i == 0)
            cout << s[i];

        // If it is the last word of the string
        // then also print it.
        if (i == s.length() - 1)
            cout << s[i];

        // If there is a space
        // print the successor and predecessor
        // to space.
        if (s[i] == ' ')
        {
            cout << s[i - 1] << " " << s[i + 1];
        }
    }
}

int main()
{
    string s = "Geeks for geeks";
    FirstAndLast(s);
}

Java

public class GfG {
    public static void firstAndLast(String s)
    {
        for (int i = 0; i < s.length(); i++) {
            
            // If it is the first character of the string
            if (i == 0) {
                System.out.print(s.charAt(i));
            }

            // If it is the last character of the string
            if (i == s.length() - 1) {
                System.out.print(s.charAt(i));
            }

            // If there is a space, print the predecessor
            // and successor
            if (s.charAt(i) == ' ') {
                System.out.print(s.charAt(i - 1));
                System.out.print(" ");
                System.out.print(s.charAt(i + 1));
            }
        }
    }

    public static void main(String[] args)
    {
        String s = "Geeks for geeks";
        firstAndLast(s);
    }
}

Python

def FirstAndLast(s):

    # Split the string into words by spaces
    words = s.split()

    for word in words:

        # Print the first and last character of each word
        if len(word) == 1:

            # If the word is a single character, print it twice
            print(word[0], end=' ')
        else:

            # Print first and last character
            print(word[0] + word[-1], end=' ')


s = "Geeks for geeks"
FirstAndLast(s)

using System;

class GfG
{
    static void FirstAndLast(string s)
    {
        for (int i = 0; i < s.Length; i++)
        {
            // If it is the first character of the string
            if (i == 0)
                Console.Write(s[i]);

            // If it is the last character of the string
            if (i == s.Length - 1)
                Console.Write(s[i]);

            // If there is a space, print the predecessor and successor
            if (s[i] == ' ')
            {
                Console.Write(s[i - 1]);
                Console.Write(" ");
                Console.Write(s[i + 1]);
            }
        }
    }

    static void Main()
    {
        string s = "Geeks for geeks";
        FirstAndLast(s);
    }
}

JavaScript

function FirstAndLast(s)
{
    // Split the string into words
    let words = s.split(" ");

    // Loop through each word
    for (let i = 0; i < words.length; i++) {
        let word = words[i];

        // If the word has only one character, print it
        // twice
        if (word.length === 1) {
            process.stdout.write(word + " ");
        }
        else {

            // Print the first and last character of the
            // word
            process.stdout.write(
                word[0] + word[word.length - 1] + " ");
        }
    }
}

let s = "Geeks for geeks";
FirstAndLast(s);

Output

Gs fr gs

Time Complexity: O(n)
Auxiliary Space: O(1)

[Approach 2]Using Built-in Functions - O(n) time and O(1) space

Use stream-based functions (like stringstream in C++) to separate the string into words.
For each word, print its first and last character. If a word contains only one character, print it twice (as both the first and last character).

C++

#include <iostream>
#include <sstream>
using namespace std;

void FirstAndLast(string s)
{
    // Split the string into words using stringstream
    stringstream ss(s);

    string word;
    while (ss >> word)
    {
        // Print the first and last character of the word
        cout << word[0] << word[word.length() - 1] << " ";
    }
}

int main()
{
    string s = "Geeks for geeks";
    FirstAndLast(s);
}