URLify a given string (Replace spaces with %20)

Given a string s, replace all the spaces in the string with '%20'.

Examples: 

Input: s = "i love programming"
Output: i%20love%20programming
Explanation: The 2 spaces are replaced by '%20'

Input: s = "ab cd"
Output: ab%20cd

[Approach] Traverse the String - O(n) Time and O(n) Space

The idea is to iterate through each character of the input string and build a new string (or result container). Whenever a space character is encountered, replace it with the string "%20", otherwise append the current character as it is.

Dry run for s = "g ee ks":

1. For i = 0, 'g' is not a space, so it is appended to result, making it "g".
2. For i = 1, ' ' is a space, so "%20" is appended, making result = "g%20".
3. For i = 2, 'e' is not a space, so it is appended, making result = "g%20e".
4. For i = 3, 'e' is not a space, so it is appended, making result = "g%20ee".
5. For i = 4, ' ' is a space, so "%20" is appended, making result = "g%20ee%20".
6. For i = 5, 'k' is not a space, so it is appended, making result = "g%20ee%20k".
7. For i = 6, 's' is not a space, so it is appended, making result = "g%20ee%20ks".

Traversal is complete, so the final result "g%20ee%20ks" is returned.

#include <iostream>
using namespace std;

string URLify(string& s) {
    
    string result = "";
    
	for (int i = 0; i < s.length(); i++) {
	    
	    // if " " is encountered, 
	    // append "%20" to string
		if (s[i] == ' ') {
		    result += "%20";
		}
		
		// else append the current 
		// character.
		else {
		    result += s[i];
		}
	}

	return result;
}

int main() {
	string s = "i love programming";
	cout << URLify(s);
	return 0;
}

class GfG {
    
    static String URLify(String s) {

        StringBuilder result = new StringBuilder();
        
        for (int i = 0; i < s.length(); i++) {
            
            // if " " is encountered, 
	        // append "%20" to string
            if (s.charAt(i) ==' ') {
                result.append("%");
                result.append("2");
                result.append("0");
            } 
            
            // else append the current 
		    // character.
            else {
                result.append(s.charAt(i));
            }
        }
        return result.toString();
    }

    public static void main(String[] args) {
        String s = "i love programming";
        System.out.println(URLify(s));
    }
}

def URLify(s) :
    n = len(s)
    
    # Use a list to mimic 
    # push_back behavior efficiently
    result = []
    
    for i in range(n):
        
        # if " " is encountered, 
        # append "%20" to the list
        if s[i] == ' ':
            result.append('%')
            result.append('2')
            result.append('0')
        
        # else append the current 
        # character.
        else:
            result.append(s[i])
            
    # Join the list into a single string at the end
    return "".join(result)

if __name__ == "__main__":
    s = "i love programming"
    print(URLify(s))

using System;
using System.Text;

public class GfG
{
    static string URLify(string s) {
        StringBuilder result = new StringBuilder();
    
        for (int i = 0; i < s.Length; i++) {
            
            // if " " is encountered, 
	        // append "%20" to string
            if (s[i] == ' ')
                result.Append("%20");
            
            // else append the current 
		    // character.
            else
                result.Append(s[i]);
        }
    
        return result.ToString();
    }

    public static void Main()
    {
        string s = "i love programming";
        Console.WriteLine(URLify(s));
    }
}

function URLify(s) {
    let result = [];

    for (let i = 0; i < s.length; i++) {
        
        // if " " is encountered, 
	    // append "%20" to string
        if (s[i] === ' ') {
            result.push('%', '2', '0');
        } else {
            result.push(s[i]);
        }
    }
    
    return result.join('');
}

// Driver Code
let s = 'i love programming';
console.log(URLify(s));

i%20love%20programming