Codility Lessons

Codility lessons solutions solved in Swift 4.2

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Lesson 1 - Iterations

• BinaryGap: Find longest sequence of zeros in binary representation of an integer.

Lesson 2 - Arrays

• OddOccurrencesInArray: Find value that occurs in odd number of elements.
• CyclicRotation: Rotate an array to the right by a given number of steps.

Lesson 3 - Time Complexity

• FrogJmp: Count minimal number of jumps from position X to Y.
• PermMissingElem: Find the missing element in a given permutation.
• TapeEquilibrium: Minimize the value |(A[0] + ... + A[P-1]) - (A[P] + ... + A[N-1])|.

Lesson 4 - Counting Elements

• PermCheck: Check whether array A is a permutation.
• FrogRiverOne: Find the earliest time when a frog can jump to the other side of a river.
• MissingInteger: Find the minimal positive integer not occurring in a given sequence.
• MaxCounters: Calculate the values of counters after applying all alternating operations: increase counter by 1; set value of all counters to current maximum.

Lesson 5 - Prefix Sums

• PassingCars: Count the number of passing cars on the road.
• GenomicRangeQuery: Find the minimal nucleotide from a range of sequence DNA.
• MinAvgTwoSlice: Find the minimal average of any slice containing at least two elements.
• CountDiv: Compute number of integers divisible by k in range [a..b].

Lesson 6 - Sorting

• Distinct: Compute number of distinct values in an array.
• MaxProductOfThree: Maximize A[P] * A[Q] * A[R] for any triplet (P, Q, R).
• Triangle: Determine whether a triangle can be built from a given set of edges.
• NumberOfDiscIntersections: Compute the number of intersections in a sequence of discs.

Lesson 7 - Stacks and Queues

• Brackets: Determine whether a given string of parentheses is properly nested.
• Fish: N voracious fish are moving along a river. Calculate how many fish are alive.
• Nesting: Determine whether given string of parentheses is properly nested.
• StoneWall: Cover "Manhattan skyline" using the minimum number of rectangles.

Lesson 8 - Leader

• EquiLeader: Find the index S such that the leaders of the sequences A[0], A[1], ..., A[S] and A[S + 1], A[S + 2], ..., A[N - 1] are the same.
• Dominator: Find an index of an array such that its value occurs at more than half of indices in the array.

Lesson 9 - Maximum slice problem

• MaxSliceSum: Find a maximum sum of a compact subsequence of array elements.
• MaxProfit: Given a log of stock prices compute the maximum possible earning.
• MaxDoubleSliceSum: Find the maximal sum of any double slice.

Lesson 10 - Prime and composite numbers

• CountFactors: Count factors of given number n.
• MinPerimeterRectangle: Find the minimal perimeter of any rectangle whose area equals N.
• Peaks: Divide an array into the maximum number of same-sized blocks, each of which should contain an index P such that A[P - 1] < A[P] > A[P + 1].
• Flags: Find the maximum number of flags that can be set on mountain peaks.

Lesson 11 - Sieve of Eratosthenes

• CountSemiprimes: Count the semiprime numbers in the given range [a..b].
• CountNonDivisible: Calculate the number of elements of an array that are not divisors of each element.

Lesson 12 - Euclidean algorithm

• ChocolatesByNumbers: There are N chocolates in a circle. Count the number of chocolates you will eat.
• CommonPrimeDivisors: Check whether two numbers have the same prime divisors.

Lesson 13 - Fibonacci numbers

• Ladder: Count the number of different ways of climbing to the top of a ladder.
• FibFrog: Count the minimum number of jumps required for a frog to get to the other side of a river.

Lesson 14 - Binary search algorithm

• MinMaxDivision: Divide array A into K blocks and minimize the largest sum of any block.
• NailingPlanks: Count the minimum number of nails that allow a series of planks to be nailed.

Lesson 15 - Caterpillar method

• CountDistinctSlices: Count the number of distinct slices (containing only unique numbers).
• CountTriangles: Count the number of triangles that can be built from a given set of edges.
• AbsDistinct: Compute number of distinct absolute values of sorted array elements.
• MinAbsSumOfTwo: Find the minimal absolute value of a sum of two elements.

Lesson 16 - Greedy algorithms

• MaxNonoverlappingSegments: Find a maximal set of non-overlapping segments.
• TieRopes: Tie adjacent ropes to achieve the maximum number of ropes of length >= K.

Lesson 17 - Dynamic programming

• NumberSolitaire: In a given array, find the subset of maximal sum in which the distance between consecutive elements is at most 6.
• MinAbsSum: Given array of integers, find the lowest absolute sum of elements.

Lesson 90 - Tasks from Indeed Prime 2015 challenge

• LongestPassword: Given a string containing words, find the longest word that satisfies specific conditions.
• FloodDepth: Find the maximum depth of water in mountains after a huge rainfall.
• SlalomSkiing: Given a sequence, find the longest subsequence that can be decomposed into at most three monotonic parts.

Lesson 91 - Tasks from Indeed Prime 2016 challenge

• RectangleBuilderGreaterArea: Count the distinct rectangle sizes, of area greater than or equal to X, that can be built out of a given set of segments.
• TreeProduct: Remove at most two edges from a tree graph to maximize the product of the components' sizes.
• HilbertMaze: Find the shortest path between two fields in a Hilbert maze.
• DwarfsRafting: Find out how many dwarfs can fit on a raft such that it's balanced when crossing a river.

Lesson 92 - Tasks from Indeed Prime 2016 College Coders challenge

• TennisTournament: Given the numbers of players and available courts, calculate the maximum number of parallel tennis games.
• SocksLaundering: From drawers containing both clean and dirty socks, choose socks to launder in order to obtain the maximum number of clean pairs of socks.
• ArrayRecovery: Recover a broken array using partial information in another array.
• DiamondsCount: Given points on a plane, count the number of sets of four points that form regular diamonds.

Lesson 99 - Future training

• SqlSum: Calculate sum of elements.
• StrSymmetryPoint: Find a symmetry point of a string, if any.
• TreeHeight: Compute the height of a binary tree.
• ArrayInversionCount: Compute number of inversion in an array.
• PolygonConcavityIndex: Check whether a given polygon in a 2D plane is convex; if not, return the index of a vertex that doesn't belong to the convex hull.