Question

Write a Java method that takes an array of char and a String as input parameters and and returns an boolean. The method returns true if we can find the input string inside the array by starting at any position of the array and reading either forwards or backwards.

Answer 1

Solution :

Steps for the program :

• To check if the given string is present in char array either forwards or backwards. We can individually check for the given string and its reverse string, if they any one of them is present in the char array, return true else return false.
• To check if a given string is present in char array, we can simply use indexOf() function, it returns the index of the where the given string is present in the char array.
• If string is not present in the char array, it returns -1
• To test the program, I have used 3 cases : case when string is present forwards, case in which string is present backwards, case in which string is not present at all.

Following is the Java program for the same :

public class solve {
    public static boolean isPresent(char[] charArray, String s)
    {   //This string will store reverse of string s 
        String rev="";  
        for(int i=s.length()-1;i>=0;i--){  
        rev+=s.charAt(i);  
    }  
        // Check for the condition for forward string and backward string
        if (new String(charArray).indexOf(s) == -1 &&  new String(charArray).indexOf(rev) == -1)
            return false;   //string is not present
        else return true;   //string is present
    }
    public static void main(String args[]) {
      //Testing
      
      //Test 1
      String s1="Programmer";
      char []array1={'c','d','P','r' , 'o' , 'g' , 'r' , 'a' , 'm' , 'm' , 'e' , 'r' , 'e' , 'H' , 'A' , 'S'};
      if(isPresent(array1,s1))
      System.out.println("Given string is present in the char array!");
      else System.out.println("Given string is not present in the char array (forwards and backwards)!");
      
      //Test 2
      String s2="Hello World!";
      char []array2={'c','d','!','d' , 'l' , 'r' , 'o' , 'W' , ' ' , 'o' , 'l' , 'l' , 'e' , 'H' , 'A' , 'S'};
      if(isPresent(array2,s2))
      System.out.println("Given string is present in the char array!");
      else System.out.println("Given string is not present in the char array (forwards and backwards)!");
      
      //Test 3
      String s3="Thank You";
      char []array3={'f','u','e','r' , '-' , 'r' , 'h' , 'T' , ' ' , 'o' , 'l' , 'l' , 'e' , 'Y' , 'O' , 'U'};
      if(isPresent(array3,s3))
      System.out.println("Given string is present in the char array!");
      else System.out.println("Given string is not present in the char array (both forwards and backwards)!");
    }
}

Code demo :

Output :