# Reverse the given string in the range [L, R]

Given a string str, and two integers L and R, the task is to reverse the string in the range [L, R] i.e. str[L…R].

Examples:

Input: str = “geeksforgeeks”, L = 5, R = 7
Output: geeksrofgeeks
Reverse the characters in the range str[5…7] = “geeksforgeeks”
and the new string will be “geeksrofgeeks”

Input: str = “ijklmn”, L = 1, R = 2
Output: ikjlmn

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach:

1. If the range is invalid i.e. either L < 0 or R ≥ len or L > R then print the original string.
2. If the range is valid then keep swapping the characters str[L] and str[R] while L < R and update L = L + 1 and R = R – 1 after every swap operation. Print the updated string in the end.

Below is the implementation of the above approach:

## C++

 // C++ implementation of the approach #include using namespace std;    // Function to return the string after // reversing characters in the range [L, R] string reverse(string str, int len, int l, int r) {        // Invalid range     if (l < 0 || r >= len || l > r)         return str;        // While there are characters to swap     while (l < r) {            // Swap(str[l], str[r])         char c = str[l];         str[l] = str[r];         str[r] = c;            l++;         r--;     }        return str; }    // Driver code int main() {     string str = "geeksforgeeks";     int len = str.length();     int l = 5, r = 7;        cout << reverse(str, len, l, r);        return 0; }

## Java

 // Java implementation of the approach import java.util.*;    class GFG {            // Function to return the string after     // reversing characters in the range [L, R]     static String reverse(char[] str, int len,                                int l, int r)     {            // Invalid range         if (l < 0 || r >= len || l > r)             return "Invalid range!";            // While there are characters to swap         while (l < r)         {                // Swap(str[l], str[r])             char c = str[l];             str[l] = str[r];             str[r] = c;                l++;             r--;         }         String string = new String(str);         return string;     }        // Driver code     public static void main (String[] args)      {         String str = "geeksforgeeks";         int len = str.length();         int l = 5, r = 7;            System.out.println(reverse(str.toCharArray(),                                           len, l, r));     } }    // This code is contributed by Ashutosh450

## Python3

 # Python3 implementation of the approach     # Function to return the string after  # reversing characters in the range [L, R]  def reverse(string, length, l, r) :        # Invalid range      if (l < 0 or r >= length or l > r) :         return string;                string = list(string)            # While there are characters to swap      while (l < r) :            # Swap(str[l], str[r])          c = string[l];          string[l] = string[r];          string[r] = c;             l += 1;          r -= 1;         return "".join(string);     # Driver code  if __name__ == "__main__" :         string = "geeksforgeeks";      length = len(string);      l = 5; r = 7;         print(reverse(string, length, l, r));     # This code is contributed by AnkitRai01

## C#

 // C# implementation of the approach using System;        class GFG {            // Function to return the string after     // reversing characters in the range [L, R]     static String reverse(char[] str, int len,                           int l, int r)     {            // Invalid range         if (l < 0 || r >= len || l > r)             return "Invalid range!";            // While there are characters to swap         while (l < r)         {                // Swap(str[l], str[r])             char c = str[l];             str[l] = str[r];             str[r] = c;                l++;             r--;         }         return String.Join("",str);     }        // Driver code     public static void Main (String[] args)      {         String str = "geeksforgeeks";         int len = str.Length;         int l = 5, r = 7;            Console.WriteLine(reverse(str.ToCharArray(),                                          len, l, r));     } }    // This code is contributed by 29AjayKumar

Output:

geeksrofgeeks

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