Solved

count7 challenge

Posted on 2016-09-09
12
69 Views
Last Modified: 2016-10-11
Hi,

I am working on below challenge

http://codingbat.com/prob/p101409


Given a non-negative int n, return the count of the occurrences of 7 as a digit, so for example 717 yields 2. (no loops). Note that mod (%) by 10 yields the rightmost digit (126 % 10 is 6), while divide (/) by 10 removes the rightmost digit (126 / 10 is 12).

count7(717) → 2
count7(7) → 1
count7(123) → 0

Not clear on how to get 7 count recursively. please advisde
0
Comment
Question by:gudii9
  • 6
  • 5
12 Comments
 
LVL 17

Assisted Solution

by:Pawan Kumar Khowal
Pawan Kumar Khowal earned 250 total points
ID: 41792254
Enjoy :)

--

DECLARE @intValue AS VARCHAR(10) = '1717E7'
 
SELECT SUM( CASE WHEN SUBSTRING(@intValue,number,1) LIKE '[7]' THEN 1 ELSE 0 END ) Count7DIGITS FROM
( 
  SELECT DISTINCT number FROM
  MASTER..SPT_VALUES WHERE number > 0 AND number <= DATALENGTH(@intValue) 
) x

--

Open in new window

0
 
LVL 27

Accepted Solution

by:
rrz earned 250 total points
ID: 41792664
CodingBat gave you the operations you need to use.
Since the challenge asks us to return a count, we can have the "base case" return 0 and not affect the count.
0
 
LVL 7

Author Comment

by:gudii9
ID: 41793654
public int count7(int n) {
  if (n < 1) {
    return 0;
  }
  if ((n % 10) == 7){ return 1 + count7(n/10);
  }
  else {
  return count7(n/10);
  }
}

Open in new window


above pass all. any improvement and alternate approaches?
0
 
LVL 27

Expert Comment

by:rrz
ID: 41793727
That is good. My solution is the same as yours.
0
 
LVL 7

Author Comment

by:gudii9
ID: 41796948
if then if then else
in above fashion code is there else belong to top if or second(last if in this case)?

public int count7(int n) {
  if (n < 1) {//else belongs to this if ??
    return 0;
  }
  if ((n % 10) == 7){ return 1 + count7(n/10);//below else belongs to this if or above if?
  }
 [b] else {
  return count7(n/10);
  }[/b]

Open in new window

}
0
 
LVL 27

Expert Comment

by:rrz
ID: 41797003
The else block is for the second if
0
How to run any project with ease

Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
- Combine task lists, docs, spreadsheets, and chat in one
- View and edit from mobile/offline
- Cut down on emails

 
LVL 7

Author Comment

by:gudii9
ID: 41798174
The else block is for the second if
how we know. is that is rule always else belong to its immediate top if not topmost if?
0
 
LVL 27

Expert Comment

by:rrz
ID: 41798326
how we know. is that is rule
Please read  
https://docs.oracle.com/javase/specs/jls/se8/html/jls-14.html#jls-14.9    
It is called
The if-then-else Statement.  
The "else" is always associated with the "if" that proceeds it.
0
 
LVL 7

Author Comment

by:gudii9
ID: 41798335
oh
https://docs.oracle.com/javase/specs/jls/se8/html/jls-14.html#jls-14.9
as per above link
IfThenStatement:
if ( Expression ) Statement
IfThenElseStatement:
if ( Expression ) StatementNoShortIf else Statement
IfThenElseStatementNoShortIf:
if ( Expression ) StatementNoShortIf else StatementNoShortIf
what is StatementNoShortIf
is there something like shortif and lognif?
0
 
LVL 27

Expert Comment

by:rrz
ID: 41798424
what is StatementNoShortIf
That is confusing.  I can't really explain why they wrote that. But, it is linked to
https://docs.oracle.com/javase/specs/jls/se8/html/jls-14.html#jls-14.5
0
 
LVL 7

Author Comment

by:gudii9
ID: 41798488
The "else" is always associated with the "if" that proceeds it.

in that link where they mentioned above point?

14.9.2. The if-then-else Statement

An if-then-else statement is executed by first evaluating the Expression. If the result is of type Boolean, it is subject to unboxing conversion (§5.1.8).

If evaluation of the Expression or the subsequent unboxing conversion (if any) completes abruptly for some reason, then the if-then-else statement completes abruptly for the same reason.

Otherwise, execution continues by making a choice based on the resulting value:

If the value is true, then the first contained Statement (the one before the else keyword) is executed; the if-then-else statement completes normally if and only if execution of that statement completes normally.

If the value is false, then the second contained Statement (the one after the else keyword) is executed; the if-then-else statement completes normally if and only if execution of that statement completes normally.

14.10. The assert Statement

That is confusing.
not sure either on  what they meant by unboxing in above context?
0
 
LVL 27

Expert Comment

by:rrz
ID: 41798613
not sure either on  what they meant by unboxing in above context?
They reference (§5.1.8). Which is at  
https://docs.oracle.com/javase/specs/jls/se8/html/jls-5.html#jls-5.1.8  
or maybe it is better explained at  
https://docs.oracle.com/javase/tutorial/java/data/autoboxing.html
0

Featured Post

Do You Know the 4 Main Threat Actor Types?

Do you know the main threat actor types? Most attackers fall into one of four categories, each with their own favored tactics, techniques, and procedures.

Join & Write a Comment

In this post we will learn how to connect and configure Android Device (Smartphone etc.) with Android Studio. After that we will run a simple Hello World Program.
International Data Corporation (IDC) prognosticates that before the current the year gets over disbursing on IT framework products to be sent in cloud environs will be $37.1B.
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

706 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

15 Experts available now in Live!

Get 1:1 Help Now