# 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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