Java program to swap first and last characters of words in a sentence

Write a Java Program to Swap first and last character of words in a Sentence as mentioned in the example? Examples:

Input : geeks for geeks
Output :seekg rof seekg

Approach:As mentioned in the example we have to replace first and last character of word and keep rest of the alphabets as it is.

• First we will create an Char array of given String by using toCharArray() method.
• Now we iterate the char array by using for loop.
• In for loop, we declare a variable whose value is dependent on i.
• Whenever we found an alphabet we increase the value of i and whenever we reach at space, we are going to perform swapping between first and last character of the word which is previous of space.

Implementation:

JAVA

class SwapFirstLastCharacters {
    static String count(String str)
    {
        // Create an equivalent char array
        // of given string
        char[] ch = str.toCharArray();
        for (int i = 0; i < ch.length; i++) {

            // k stores index of first character
            // and i is going to store index of last
            // character.
            int k = i;
            while (i < ch.length && ch[i] != ' ')
                i++;

            // Swapping
            char temp = ch[k];
            ch[k] = ch[i - 1];
            ch[i - 1] = temp;

            // We assume that there is only one space
            // between two words.
        }
        return new String(ch);
    }
    public static void main(String[] args)
    {
        String str = "geeks for geeks";
        System.out.println(count(str));
    }
}

Output

seekg rof seekg

Time complexity: O(n) where n is the length of the given input string

Auxiliary space: O(n)