Program for length of a string using recursion

Given a string calculate length of the string using recursion. 

Examples: 

Input: str = "abcd"
Output: 4
Explanation: The string "abcd" has a length of 4.

Input: str = "GEEKSFORGEEKS"
Output: 13

We have also covered this topic—feel free to check it out as well
5 Different methods to find length of a string in C++ 
How to find length of a string without string.h and loop in C?

Approach:

If the string is empty (""), the function returns 0 since there are no characters left to count. Otherwise, the first character is removed using substring(1), reducing the string size by one. The function then recursively calls itself on the remaining substring. With each recursive call, 1 is added to the result to account for the removed character. This process continues until the string becomes empty, at which point the recursion stops.

#include <bits/stdc++.h>
using namespace std;

int recLen(string str)
{
    // Base case: If the string is empty
    if (str == "")
        return 0;
    return 1 + recLen(str.substr(1));
}

// Driver code
int main()
{
    string str = "GeeksforGeeks";
    cout << recLen(str) << endl;
    return 0;
}

import java.util.*;

public class GfG {

    static int recLen(String str)
    {
        if (str.equals(""))
            return 0;
        else
            return recLen(str.substring(1)) + 1;
    }

    /* Driver program to test above function */
    public static void main(String[] args)
    {
        String str = "GeeksforGeeks";
        System.out.println(recLen(str));
    }
}

def recLen(str):
    # Base case: If the string is empty
    if str == "":
        return 0
    return 1 + recLen(str[1:])


# Driver code
str = "GeeksforGeeks"
print(recLen(str)) 

using System;

class GfG {
    static int recLen(string str)
    {
        // Base case: If the string is empty
        if (str == "")
            return 0;
        return 1 + recLen(str.Substring(1));
    }

    static void Main()
    {
        string str = "GeeksforGeeks";
        Console.WriteLine(recLen(str));
    }
}

function recLen(str)
{
    // Base case: If the string is empty
    if (str === "")
        return 0;
    return 1 + recLen(str.substring(1));
}

// Driver code
let str = "GeeksforGeeks";
console.log(recLen(str)); // Output: 13

13

Time Complexity: O(n²), where n is the length of the string.
Auxiliary Space: O(n²)

Note: This approach is inefficient as it requires extra space, incurs function call overhead, and runs in O(n²) time, making it impractical for large inputs.