What is wrong in my code?

#1

package STRINGS;

import java.util.Scanner;

public class findingcbnumbers {

public static void main(String[] args) {
	Scanner scn = new Scanner(System.in);
	int n = scn.nextInt();
	String str="";
    for (int i=0;i<n;i++) {
    	String s=scn.next();
    	str=str+s;
    }
    cbno(str,1);
   
}
public static void cbno(String str,int vidx) {
	int count=0;
	if (vidx>=str.length()) {
		System.out.println(count);
	}
	
	for (int i=vidx;i<str.length();i++) {
		String a=str.substring(0,i);
		int a1=Stringtointeger( a,0);
		if (a1%2 !=0 && a1%3 !=0) {
			count++;
		}
	}
	cbno(str,vidx+1);
}
public static int Stringtointeger(String str,int lo) {
	int ch=0;
	if (lo>=str.length()) {
		return ch;
	}
	
	 ch=ch+str.charAt(lo)-'0';
	
	Stringtointeger(str,lo+1);
	return ch;
}

}

#2

@harsh.hj,
Suggested approach:

  1. check for all sub-strings of the given string of digits, starting from the all strings of length 1 and then gradually checking for the strings of increasing size:

1.1. check if the sub-string is CB number: for this, create a function
1.1.1. if sub-string is 1 or 0 return false.
1.1.2. if sub-string is any of the {2,3,5,7,11,13,17,19,23,29}, then return true.
1.1.3. if sub-string is divisible by any of the {2,3,5,7,11,13,17,19,23,29}, then return false.
1.1.4. return false

1.2. now if it is a substring:
1.2.1. call a function that marks the index as visited for indexes which are part of that CB number.

1.3. increment the count for CB number.

  1. Print the count
#3

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