Remove first and last characters

Given a string s, return a substring containing all characters except the first and the last. The length of the s will be greater than 2.

Examples:

Input: s = "Hello"
Output: ell
Explanation: The first and last character are ignored.

Input: s = "World"
Output: orl
Explanation: The first and last characters are ignored.

Try It Yourself

Table of Content

Using Character Traversal - O(n) Time O(n) Space
Using Built-in Substring/Slicing Function - O(n) Time and O(n) Space

Using Character Traversal - O(n) Time O(n) Space

The idea is to traverse the string from the second character to the second-last character and append each character to a new string. This new string will contain all characters except the first and last ones.

C++

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

// Function to return the sliced string
string sliceString(string &s)
{

    // Stores the resultant substring
    string res = "";

    // Traverse from second character to second-last character
    for (int i = 1; i < (int)s.length() - 1; i++)
    {
        res += s[i];
    }

    return res;
}

// Driver Code
int main()
{
    string s = "World";

    cout << sliceString(s);

    return 0;
}

#include <stdio.h>
#include <string.h>

// Function to return the sliced string
char* sliceString(char* s)
{
    // Stores the resultant substring
    char res[100] = "";
    int j = 0;

    // Traverse from second character to second-last character
    for (int i = 1; i < strlen(s) - 1; i++)
    {
        res[j++] = s[i];
    }
    res[j] = '\0';

    return strdup(res);
}

// Driver Code
int main()
{
    char s[] = "World";
    char* result = sliceString(s);
    printf("%s", result);
    free(result);
    return 0;
}

Java

public class GfG {
    // Function to return the sliced string
    public static String sliceString(String s)
    {
        // Stores the resultant substring
        String res = "";

        // Traverse from second character to second-last
        // character
        for (int i = 1; i < s.length() - 1; i++) {
            res += s.charAt(i);
        }

        return res;
    }

    // Driver Code
    public static void main(String[] args)
    {
        String s = "World";
        System.out.println(sliceString(s));
    }
}

Python

# Function to return the sliced string
def sliceString(s):
    # Stores the resultant substring
    res = ""

    # Traverse from second character to second-last character
    for i in range(1, len(s) - 1):
        res += s[i]

    return res


# Driver Code
if __name__ == "__main__":
    s = "World"

    print(sliceString(s))

using System;

public class GfG {
    // Function to return the sliced string
    public static string sliceString(string s)
    {
        // Stores the resultant substring
        string res = "";

        // Traverse from second character to second-last
        // character
        for (int i = 1; i < s.Length - 1; i++) {
            res += s[i];
        }

        return res;
    }

    // Driver Code
    public static void Main()
    {
        string s = "World";
        Console.WriteLine(sliceString(s));
    }
}

JavaScript

// Function to return the sliced string
function sliceString(s) {
    // Stores the resultant substring
    let res = "";

    // Traverse from second character to second-last character
    for (let i = 1; i < s.length - 1; i++) {
        res += s[i];
    }

    return res;
}

// Driver Code
let s = "World";
console.log(sliceString(s));

Output

orl

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

Using Built-in Substring/Slicing Function - O(n) Time and O(n) Space

The idea is to directly use the built-in substring/slicing function provided by the language. Since we need to ignore the first and last characters, we start from index 1 and take length - 2 characters.

Built-in Substring/Slicing Functions in Different Languages:

C does not provide a built-in string slicing function. We can use functions like strncpy() to copy the required portion of the string into a new character array.
The substring starts from index 1 and has length strlen(s) - 2.

C++:

C++ provides the substr() function of the string class to extract a substring.
We can directly use s.substr(1, s.length() - 2) to remove the first and last characters.

Python:

Python supports string slicing using the slice operator [:].
The expression s[1:-1] returns all characters except the first and the last.

JavaScript:

JavaScript provides methods such as slice() and substring() for extracting substrings.
The required substring can be obtained using s.slice(1, -1), which excludes the first and last characters.

Java:

Java provides the substring() method of the String class for extracting a part of a string.
The required substring can be obtained using s.substring(1, s.length() - 1).

C#:

C# provides the Substring() method of the String class.
We can start from index 1 and extract s.Length - 2 characters using s.Substring(1, s.Length - 2).

C++

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

// Function to return the sliced string
string sliceString(string &s)
{

    // Extract substring excluding first and last character
    return s.substr(1, s.length() - 2);
}

// Driver Code
int main()
{
    string s = "World";

    cout << sliceString(s);

    return 0;
}

#include <stdio.h>
#include <string.h>

// Function to return the sliced string
char* sliceString(char* s)
{
    static char result[100];
    strncpy(result, s + 1, strlen(s) - 2);
    result[strlen(s) - 2] = '\0';
    return result;
}

// Driver Code
int main()
{
    char s[] = "World";
    printf("%s", sliceString(s));
    return 0;
}