Function to copy string (Iterative and Recursive)

Given two strings, copy one string to another using recursion. We basically need to write our own recursive version of strcpy in C/C++

Examples:

Input : s1 = "hello"
        s2 = "geeksforgeeks"
Output : s2 = "hello"

Input :  s1 = "geeksforgeeks"
         s2 = ""
Output : s2 = "geeksforgeeks"

Iterative: Copy every character from s1 to s2 starting from index = 0 and in each call increase the index by 1 until s1 doesn’t reach to end; 

Implementation:

C++

// Iterative CPP Program to copy one String
// to another.
#include <bits/stdc++.h>
using namespace std;

// Function to copy one string to other
// assuming that other string has enough
// space.
void myCopy(char s1[], char s2[])
{
    int i = 0;
    for (i=0; s1[i] != '\0'; i++)
       s2[i] = s1[i];
    s2[i] = '\0';
}

// Driver function
int main()
{
    char s1[100] = "GEEKSFORGEEKS";
    char s2[100] = "";
    myCopy(s1, s2);
    cout << s2;
    return 0;
}

Java

// Iterative Java Program to copy one String
// to another.
class GFG
{

// Function to copy one string to other
// assuming that other string has enough
// space.
static void myCopy(char s1[], char s2[])
{
    int i = 0;
    for (i = 0; i < s1.length; i++)
         s2[i] = s1[i];
}

// Driver code
public static void main(String[] args)
{
    char s1[] = "GEEKSFORGEEKS".toCharArray();
    char s2[] = new char[s1.length];
    myCopy(s1, s2);
    System.out.println(String.valueOf(s2));
}
}

// This code contributed by Rajput-Ji

Python3

## Iterative Python Program to copy one String
# to another.
# Function to copy one string to other
def myCopy(s1,s2):
    # traversing the string s1 from start to end
    for i in range(len(s1)):
        # copying value one by one
        s2[i]=s1[i]
    return "".join(s2)

#Driver code
s1=list("GEEKSFORGEEKS")
s2=[""]*len(s1)
print(myCopy(s1,s2))
'''Code is contributed by RAJAT KUMAR (rajatkumargla19)'''

C#

// Iterative C# Program to copy one String
// to another.
using System;

class GFG
{

// Function to copy one string to other
// assuming that other string has enough
// space.
static void myCopy(char []s1, char []s2)
{
    int i = 0;
    for (i = 0; i < s1.Length; i++)
        s2[i] = s1[i];
}

// Driver code
public static void Main(String[] args)
{
    char []s1 = "GEEKSFORGEEKS".ToCharArray();
    char []s2 = new char[s1.Length];
    myCopy(s1, s2);
    Console.WriteLine(String.Join("", s2));
}
}

// This code is contributed by 29AjayKumar

Javascript

<script>

// Iterative Javascript Program to copy one String
// to another.

// Function to copy one string to other
// assuming that other string has enough
// space.
function myCopy(s1, s2)
{
    let i = 0;
    for (i = 0; i < s1.length; i++)
         s2[i] = s1[i];
}

// Driver code
    // Driver Code
let s1 = "GEEKSFORGEEKS";
let s2 = [];
let index = 0;

myCopy(s1, s2, index);

document.write(s2.join(""));

// This code contributed by shivanisinghss2110

</script>

Output

GEEKSFORGEEKS

Time Complexity: O(m), Here m is the length of string s1.
Auxiliary Space: O(1), As constant extra space is used.

Recursive: Copy every character from s1 to s2 starting from index = 0 and in each call increase the index by 1 until s1 doesn’t reach to end; 

Implementation:

C++

// CPP Program to copy one String to
// another using Recursion
#include <bits/stdc++.h>
using namespace std;

// Function to copy one string in to other
// using recursion
void myCopy(char s1[], char s2[], int index = 0)
{
    // copying each character from s1 to s2
    s2[index] = s1[index];

    // if string reach to end then stop
    if (s1[index] == '\0')
        return;

    // increase character index by one
    myCopy(s1, s2, index + 1);
}

// Driver function
int main()
{
    char s1[100] = "GEEKSFORGEEKS";
    char s2[100] = "";
    myCopy(s1, s2);
    cout << s2;
    return 0;
}

Java

// Java Program to copy one String to
// another using Recursion
class GFG
{

    // Function to copy one string in to other
    // using recursion
    static void myCopy(char s1[],
                       char s2[], int index)
    {
        // copying each character from s1 to s2
        s2[index] = s1[index];

        // if string reach to end then stop
        if (index == s1.length - 1)
        {
            return;
        }

        // increase character index by one
        myCopy(s1, s2, index + 1);
    }

    // Driver Code
    public static void main(String[] args)
    {
        char s1[] = "GEEKSFORGEEKS".toCharArray();
        char s2[] = new char[s1.length];
        int index = 0;
        myCopy(s1, s2, index);
        System.out.println(String.valueOf(s2));
    }
}

// This code is contributed by PrinciRaj1992

Python3

# recursive Python Program to copy one String
# to another.

# Function to copy one string to other


def copy_str(x, y):
    if len(y) == 0:
        return x
    else:
        c = copy_str(x, (y)[1:-1])
        return c


x = input("hello")
y = input("no")
print(copy_str(x, y))

# This code contributed by deeksha20049@iiid.ac.in

C#

// C# Program to copy one String to
// another using Recursion
using System;

class GFG
{

    // Function to copy one string in to other
    // using recursion
    static void myCopy(char []s1,
                       char []s2, int index)
    {
        // copying each character from s1 to s2
        s2[index] = s1[index];

        // if string reach to end then stop
        if (index == s1.Length - 1)
        {
            return;
        }

        // increase character index by one
        myCopy(s1, s2, index + 1);
    }

    // Driver Code
    public static void Main(String[] args)
    {
        char []s1 = "GEEKSFORGEEKS".ToCharArray();
        char []s2 = new char[s1.Length];
        int index = 0;
        myCopy(s1, s2, index);
        Console.WriteLine(String.Join("", s2));
    }
}

// This code is contributed by Princi Singh

Javascript

<script>

// Javascript program to copy one String to
// another using Recursion

// Function to copy one string in to other
// using recursion
function myCopy(s1, s2, index)
{

    // Copying each character from s1 to s2
    s2[index] = s1[index];

    // If string reach to end then stop
    if (index == s1.length - 1)
    {
        return;
    }

    // Increase character index by one
    myCopy(s1, s2, index + 1);
}

// Driver Code
var s1 = "GEEKSFORGEEKS";
var s2 = [];
var index = 0;

myCopy(s1, s2, index);

document.write(s2.join(""));

// This code is contributed by gauravrajput1

</script>

Output:

GEEKSFORGEEKS

Time Complexity: O(m), Here m is the length of string s1.
Auxiliary Space: O(m), due to recursive call stack