Counting Valleys | Python Solution | HackerRank

 An avid hiker keeps meticulous records of their hikes. During the last hike that took exactly  steps, for every step it was noted if it was an uphill, , or a downhill,  step. Hikes always start and end at sea level, and each step up or down represents a  unit change in altitude. We define the following terms:

• A mountain is a sequence of consecutive steps above sea level, starting with a step up from sea level and ending with a step down to sea level.
• A valley is a sequence of consecutive steps below sea level, starting with a step down from sea level and ending with a step up to sea level.

Given the sequence of up and down steps during a hike, find and print the number of valleys walked through.

Drawing Book | Python Solution | HackerRank

 A teacher asks the class to open their books to a page number. A student can either start turning pages from the front of the book or from the back of the book. They always turn pages one at a time. When they open the book, page  is always on the right side:

When they flip page , they see pages  and . Each page except the last page will always be printed on both sides. The last page may only be printed on the front, given the length of the book. If the book is  pages long, and a student wants to turn to page , what is the minimum number of pages to turn? They can start at the beginning or the end of the book.

Given  and , find and print the minimum number of pages that must be turned in order to arrive at page .

Example

Using the diagram above, if the student wants to get to page , they open the book to page , flip  page and they are on the correct page. If they open the book to the last page, page , they turn  page and are at the correct page. Return .

Sales by Match | Python Solution | HackerRank

 There is a large pile of socks that must be paired by color. Given an array of integers representing the color of each sock, determine how many pairs of socks with matching colors there are.

Example

There is one pair of color  and one of color . There are three odd socks left, one of each color. The number of pairs is .

Function Description

Complete the sockMerchant function in the editor below.

sockMerchant has the following parameter(s):

• int n: the number of socks in the pile
• int ar[n]: the colors of each sock

Day of the Programmer | Python Solution | HackerRank

 Marie invented a Time Machine and wants to test it by time-traveling to visit Russia on the Day of the Programmer (the 256th day of the year) during a year in the inclusive range from 1700 to 2700.

From 1700 to 1917, Russia's official calendar was the Julian calendar; since 1919 they used the Gregorian calendar system. The transition from the Julian to Gregorian calendar system occurred in 1918, when the next day after January 31st was February 14th. This means that in 1918, February 14th was the 32nd day of the year in Russia.

In both calendar systems, February is the only month with a variable amount of days; it has 29 days during a leap year, and 28 days during all other years. In the Julian calendar, leap years are divisible by 4; in the Gregorian calendar, leap years are either of the following:

• Divisible by 400.
• Divisible by 4 and not divisible by 100.

Given a year, , find the date of the 256th day of that year according to the official Russian calendar during that year. Then print it in the format dd.mm.yyyy, where dd is the two-digit day, mm is the two-digit month, and yyyy is .

For example, the given  = 1984. 1984 is divisible by 4, so it is a leap year. The 256th day of a leap year after 1918 is September 12, so the answer is .

Migratory Birds | Python Solution | HackerRank

 Given an array of bird sightings where every element represents a bird type id, determine the id of the most frequently sighted type. If more than 1 type has been spotted that maximum amount, return the smallest of their ids.

Example

There are two each of types  and , and one sighting of type . Pick the lower of the two types seen twice: type .

Divisible Sum Pairs | Python Solution | HackerRank

 Given an array of integers and a positive integer , determine the number of  pairs where  and  +  is divisible by.

Example

Three pairs meet the criteria:  and .

Function Description

Complete the divisibleSumPairs function in the editor below.

divisibleSumPairs has the following parameter(s):

• int n: the length of array 
• int ar[n]: an array of integers
• int k: the integer divisor