URLify a given string (Replace spaces with %20)

Given a string s, the task is to 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:

The idea is to iterate through each character of the input string and create a new string by replacing space characters with the '%20' escape sequence.

Step by step approach:

1. Iterate through each character in the input string from start to end.
2. Check if the current character is a space.
   • If a space is found, append '%20' to the result string.
   • If the current character is not a space, append the original character to the result string.
3. Return the final modified string with spaces replaced by '%20'.

// C++ program to URLify a given string
#include <bits/stdc++.h>
using namespace std;

string URLify(string& s) {
    int n = s.length();
	
	string ans = "";
	for (int i = 0; i<n; i++) {
	    
	    // If " " is encountered, 
	    // append "%20" to string
		if (s[i] == ' ') {
		    ans.push_back('%');
		    ans.push_back('2');
		    ans.push_back('0');
		}
		
		// Else append the current 
		// character.
		else {
		    ans.push_back(s[i]);
		}
	}

	return ans;
}

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

import java.util.*;

public class Main {
    public static String URLify(String s) {
        int n = s.length();
        StringBuilder ans = new StringBuilder();
        for (int i = 0; i < n; i++) {
            if (s.charAt(i) ==' ') {
                ans.append("%");
                ans.append("2");
                ans.append("0");
            } else {
                ans.append(s.charAt(i));
            }
        }
        return ans.toString();
    }

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

def urlify(s: str) -> str:
    n = len(s)
    
    # We use a list to mimic push_back behavior efficiently
    ans = []
    
    for i in range(n):
        # If " " is encountered, 
        # append "%20" to the list
        if s[i] == ' ':
            ans.append('%')
            ans.append('2')
            ans.append('0')
        
        # Else append the current 
        # character.
        else:
            ans.append(s[i])
            
    # Join the list into a single string at the end
    return "".join(ans)

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

using System;
using System.Collections.Generic;

public class Program
{
    public static string Urlify(string s)
    {
        int n = s.Length;
        List<char> ans = new List<char>();
        for (int i = 0; i < n; i++)
        {
            if (s[i] == ' ')
            {
                ans.Add('%');
                ans.Add('2');
                ans.Add('0');
            }
            else
            {
                ans.Add(s[i]);
            }
        }
        return new string(ans.ToArray());
    }

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

const program = {
  urlify: function(s) {
    let n = s.length;
    let ans = [];
    for (let i = 0; i < n; i++) {
      if (s[i] ===' ') {
        ans.push('%');
        ans.push('2');
        ans.push('0');
      } else {
        ans.push(s[i]);
      }
    }
    return ans.join('');
  },
  main: function() {
    let s = 'i love programming';
    console.log(this.urlify(s));
  }
};
program.main();

i%20love%20programming

Time Complexity: O(n), as the string is traversed only once.
Auxiliary Space: O(n), used for output string.