Code Challenge problem set of Aug 15th, 2015

Problem 1: Balanced string

“Everything should be balanced and your life is too. You could spend a lot of time for work but please save time for your family”, said by a good father Toan. “And a string should be as well, I think ToannaoT is better than my name”, he went ahead. And he invented a “balanced string” that its characters are mirrored by its center. For example, abcba or abccba are balanced while abcbc and abccbc are not.

Give you a list of string, compute the sum of length of all balanced strings.

Note: it’s also called “palindrome” which reads the same backward or forward.

Sample input:


Sample output:


Problem 2: Phone number

Cuong has a locked iPhone and it always gives him a headache of contact and phone number mapping. For example, he saved his girlfriend’s number 0987654321 to his contact, but it always shows up 84-9876-54321 as it adds the country code automatically.

As a super programmer, he of course wants to fix this by a coding service to recognize each parts and join it himself. Do you want to solve it with Cuong?

Give you a list of phone numbers, each number in each line. A phone number has a format

PhoneNumber = [CountryCode][separator][LocalAreaCode][separator][Number]


  • separator is space or hyphen
  • CountryCode, LocalAreaCode, Number only contain the digits.

Submit the result = [Sum_of_CountryCode] * [Sum_of_LocalAreaCode] * [Sum_of_Number]

Sample input:

1 877 2638277

Sample output:


Problem 3: Love letter

Yesterday, The just found a love letter that his friend, Long, has writtent to his girldfriend. As a naughty boy, he want to meddle with this letter and change all the words to “ballanced” (palindrome) that Toan has invented. But to be safe, he should follow the rule and save his steps to make this letter recoveryable later.

  • He can reduce the value of a letter but cannot increase. For example, he can change b to a but cannot change a to b.
  • Once a letter has been changed to a, it can no longer to be changed.
  • Each step, he can reduce 1 letter with 1 unit. For example, changing c to a needs 2 steps.

So let find the minimum steps for him to change this letter to palindrome.

Sample input


Sample output


Problem 4: Girl attracting law by Fibonacci approach

After a long time in-door researched, Hung found a good approach to attract a girl and he named it“Girl attracting law by Fibonacci approach” that means the number of presents Hung gives to her is increased by Fibonacci sequence. But don’t stop, he extended to version 2 with some customisation by:

T(n+2) = T(n+1) * T(n+1) + T(n)

with T(n) is a number of presents at the nth dating.

Hung of course has a lot of money but wants to trust a girl, so he should give her 0 present at the first and 1 present at the second dating. And following his theory, 5 presents should be given in the 5th dating as explanation below:

1st number  = 0

2nd number = 1

3rd number = 12 + 0 = 1

4th number = 12 + 1 = 2

5th number = 22 + 1 = 5

Hung said that he has meet her 13 times and today he wants to know how many present he should give. Could you help Hung?

These problems are modified by some in Hackerrank