Tag Archives: math

Hello Hello : CodeChef Problem HELLO

Problem link: http://www.codechef.com/AUG13/problems/HELLO/

Problem Statement:
Chef talks a lot on his mobile phone. As a result he exhausts his talk-value (in Rokdas) very quickly. One day at a mobile recharge shop, he noticed that his service provider gives add-on plans which can lower his calling rates (Rokdas/minute). One of the plans said “Recharge for 28 Rokdas and enjoy call rates of 0.50 Rokdas/min for one month”. Chef was very pleased. His normal calling rate is 1 Rokda/min. And he talked for 200 minutes in last month, which costed him 200 Rokdas. If he had this plan activated, it would have costed him: 28 + 0.5*200 = 128 Rokdas only! Chef could have saved 72 Rokdas. But if he pays for this add-on and talks for very little in the coming month, he may end up saving nothing or even wasting money. Now, Chef is a simple guy and he doesn’t worry much about future. He decides to choose the plan based upon his last month’s usage.

There are numerous plans. Some for 1 month, some for 15 months. Some reduce call rate to 0.75 Rokdas/min, some reduce it to 0.60 Rokdas/min. And of course each of them differ in their activation costs. Note – If a plan is valid for M months, then we must pay for (re)activation after every M months (once in M months). Naturally, Chef is confused, and you (as always) are given the task to help him choose the best plan.
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Splitting Candies : CodeChef Problem SPCANDY

Problem link: http://www.codechef.com/AUG13/problems/SPCANDY/

Problem Statement:
Cyael is a teacher at a very famous school in Byteland and she is known by her students for being very polite to them and also to encourage them to get good marks on their tests.

Then, if they get good marks she will reward them with candies đŸ™‚ However, she knows they are all very good at Mathematics, so she decided to split the candies evenly to all the students she considers worth of receiving them, so they don’t fight with each other.

She has a bag which initially contains N candies and she intends to split the candies evenly to K students. To do this she will proceed as follows: while she has more than K candies she will give exactly 1 candy to each student until she has less than K candies. On this situation, as she can’t split candies equally among all students she will keep the remaining candies to herself.

Your job is to tell how many candies will each student and the teacher
receive after the splitting is performed.
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Special Pythagorean triplet: Project Euler Problem 9

Problem link: http://projecteuler.net/problem=9

Problem Statement:
A Pythagorean triplet is a set of three natural numbers, a<b<c, for which,

For example, 3^2+4^2=9+16=25=5^2.

There exists exactly one Pythagorean triplet for which a + b + c = 1000.
Find the product abc.

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Summation of primes: Project Euler Problem 10

Problem link: http://projecteuler.net/problem=10

Problem Statement:
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Find the sum of all the primes below two million.

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Largest product in a series: Project Euler Problem 8

Problem link: http://projecteuler.net/problem=8

Problem Statement:
Find the greatest product of five consecutive digits in the 1000-digit number.


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Sum square difference: Project Euler Problem 6

Problem link: http://projecteuler.net/problem=6

Problem Statement:

The sum of the squares of the first ten natural numbers is,
1^2 + 2^2 + ... + 10^2 = 385

The square of the sum of the first ten natural numbers is,
(1 + 2 + ... + 10)^2 = 55^2 = 3025

Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025-385=2640.

Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.

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Unfriendly Numbers: Hackerrank

Problem link: https://www.hackerrank.com/challenges/unfriendly-numbers

Problem Statement:
There is one friendly number and N unfriendly numbers. We want to find how many numbers are there which exactly divide the friendly number, but does not divide any of the unfriendly numbers.
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