A sentence is a sequence of characters separated by some delimiter. This sequence of characters starts at the 0th index and the last index is at len(string)-1. By reversing the string, we interchange the characters starting at 0th index and place them from the end. The first character becomes the last, the second becomes the second last, and so on.
Example:
Input : Lazyroar Output: skeegrofskeeG Input : Alice Output: ecilA
Approach:
- Check if the string is empty or not, return null if String is empty.
- If the string is empty then return the null string.
- Else return the concatenation of sub-string part of the string from index 1 to string length with the first character of a string. e.g. return substring(1)+str.charAt(0); which is for string “Mayur” return will be “ayur” + “M”.
Below is the implementation of the above approach:
Java
// Java Program to Reverse a Sentence Using Recursionimport java.io.*;public class GFG { public static String reverse_sentence(String str) { // check if str is empty if (str.isEmpty()) // return the string return str; else { // extract the character at 0th index, that is // the character at beginning char ch = str.charAt(0); // append character extracted at the end // and pass the remaining string to the function return reverse_sentence(str.substring(1)) + ch; } } public static void main(String[] args) { // specify the string to reverse String str = "Geeksforgeeks"; // call the method to reverse sentence String rev_str = reverse_sentence(str); // print the reversed sentence System.out.println( "Sentence in reversed form is : " + rev_str); // creating another string with numbers // and special characters String str2 = "Alice"; String rev_str2 = reverse_sentence(str2); // print the reversed sentence System.out.println( "Sentence in reversed form is : " + rev_str2); }} |
Output
Sentence in reversed form is : skeegrofskeeG Sentence in reversed form is : ecilA
Time Complexity: O(N), where N is the length of the string.
Auxiliary Space: O(N) for call stack
