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(ns foreclojure.data-set
(:use [somnium.congomongo]))
(defn load-problems []
(do
(mongo! :db :mydb)
(insert! :problems
{:_id 1
:title "Nothing but the Truth"
:times-solved 0
:description "This is a clojure form. Enter a value which will make the form evaluate to true. Don't over think it! If you are confused, see the <a href='/directions'>getting started</a> page. Hint: true is equal to true."
:tags ["elementary"]
:tests ["(= __ true)"]})
(insert! :problems
{:_id 2
:title "Simple Math"
:times-solved 0
:description "If you are not familiar with <a href='http://en.wikipedia.org/wiki/Polish_notation'>polish notation</a>, simple arithmetic might seem confusing."
:tags ["elementary"]
:tests ["(= (- 10 (* 2 3)) __)"]})
(insert! :problems
{:_id 3
:title "Intro to Strings"
:times-solved 0
:description "Clojure strings are Java strings. This means that you can use any of the Java string methods on Clojure strings."
:tags["elementary"]
:tests ["(= __ (.toUpperCase \"hello world\"))"]})
(insert! :problems
{:_id 4
:title "Intro to Lists"
:times-solved 0
:description "Lists can be constructed with either a function or a quoted form."
:tags["elementary"]
:tests ["(= (list __) '(:a :b :c))"]})
(insert! :problems
{:_id 5
:title "Lists: conj"
:times-solved 0
:description "When operating on a list, the conj function will return a new list with one or more items \"added\" to the front."
:tags["elementary"]
:tests ["(= __ (conj '(2 3 4) 1))"
"(= __ (conj '(3 4) 2 1))"]})
(insert! :problems
{:_id 6
:title "Intro to Vectors"
:times-solved 0
:description "Vectors can be constructed several ways. You can compare them with lists."
:tags["elementary"]
:tests ["(= [__] (list :a :b :c) (vec '(:a :b :c)) (vector :a :b :c))"]})
(insert! :problems
{:_id 7
:title "Vectors: conj"
:times-solved 0
:description "When operating on a Vector, the conj function will return a new vector with one or more items \"added\" to the end."
:tags["elementary"]
:tests ["(= __ (conj [1 2 3] 4))"
"(= __ (conj [1 2] 3 4))"]})
(insert! :problems
{:_id 8
:title "Intro to Sets"
:times-solved 0
:description "Sets are collections of unique values."
:tags["elementary"]
:tests ["(= __ (set '(:a :a :b :c :c :c :c :d :d)))"
"(= __ (clojure.set/union #{:a :b :c} #{:b :c :d}))"]})
(insert! :problems
{:_id 9
:title "Sets: conj"
:times-solved 0
:description "When operating on a set, the conj function returns a new set with one or more keys \"added\"."
:tags["elementary"]
:tests ["(= #{1 2 3 4} (conj #{1 4 3} __))"]})
(insert! :problems
{:_id 10
:title "Intro to Maps"
:times-solved 0
:description "Maps store key-value pairs. Both maps and keywords can be used as lookup functions. Commas can be used to make maps more readable, but they are not required."
:tags["elementary"]
:tests ["(= __ ((hash-map :a 10, :b 20, :c 30) :b))"
"(= __ (:b {:a 10, :b 20, :c 30}))"]})
(insert! :problems
{:_id 11
:title "Maps: conj"
:times-solved 0
:description "When operating on a map, the conj function returns a new map with one or more key-value pairs \"added\"."
:tags["elementary"]
:tests ["(= {:a 1, :b 2, :c 3} (conj {:a 1} __ [:c 3]))"]})
(insert! :problems
{:_id 12
:title "Intro to Sequences"
:times-solved 0
:description "All Clojure collections support sequencing. You can operate on sequences with functions like first, second, and last."
:tags["elementary"]
:tests ["(= __ (first '(3 2 1)))"
"(= __ (second [2 3 4]))"
"(= __ (last (list 1 2 3)))"]})
(insert! :problems
{:_id 13
:title "Sequences: rest"
:times-solved 0
:description "The rest function will return all the items of a sequence except the first."
:tags["elementary"]
:tests ["(= __ (rest [10 20 30 40]))"]})
(insert! :problems
{:_id 14
:title "Intro to Functions"
:times-solved 0
:description "Clojure has many different ways to create functions."
:tags["elementary"]
:tests ["(= __ ((fn add-five [x] (+ x 5)) 3))"
"(= __ ((fn [x] (+ x 5)) 3))"
"(= __ (#(+ % 5) 3))"
"(= __ ((partial + 5) 3))"]})
(insert! :problems
{:_id 15
:title "Double Down"
:times-solved 0
:description "Write a function which doubles a number."
:tags ["elementary"]
:tests ["(= (__ 2) 4)"
"(= (__ 3) 6)"
"(= (__ 11) 22)"
"(= (__ 7) 14)"]})
(insert! :problems
{:_id 16
:title "Hello World"
:times-solved 0
:description "Write a function which returns a personalized greeting."
:tags ["elementary"]
:tests ["(= (__ \"Dave\") \"Hello, Dave!\")"
"(= (__ \"Jenn\") \"Hello, Jenn!\")"
"(= (__ \"Rhea\") \"Hello, Rhea!\")"]})
(insert! :problems
{:_id 17
:title "Sequences: map"
:times-solved 0
:description "The map function takes two arguments: a function (f) and a sequence (s). Map returns a new sequence consisting of the result of applying f to each item of s. Do not confuse the map function with the map data structure."
:tags["elementary"]
:tests ["(= __ (map #(+ % 5) '(1 2 3)))"]})
(insert! :problems
{:_id 18
:title "Sequences: filter"
:times-solved 0
:description "The filter function takes two arguments: a predicate function (f) and a sequence (s). Filter returns a new sequence consisting of all the items of s for which (f item) returns true."
:tags["elementary"]
:tests ["(= __ (filter #(> % 5) '(3 4 5 6 7)))"]})
(insert! :problems
{:_id 19
:title "Last Element"
:times-solved 0
:restricted ["last"]
:description "Write a function which returns the last element in a sequence."
:tags ["easy" "seqs" "core-functions"]
:tests ["(= (__ [1 2 3 4 5]) 5)"
"(= (__ '(5 4 3)) 3)"
"(= (__ [\"b\" \"c\" \"d\"]) \"d\")"]})
(insert! :problems
{:_id 20
:title "Penultimate Element"
:times-solved 0
:description "Write a function which returns the second to last element from a sequence."
:tags["easy" "seqs"]
:tests ["(= (__ (list 1 2 3 4 5)) 4)"
"(= (__ [\"a\" \"b\" \"c\"]) \"b\")"
"(= (__ [[1 2] [3 4]]) [1 2])"]})
(insert! :problems
{:_id 21
:title "Nth Element"
:times-solved 0
:restricted ["nth"]
:description "Write a function which returns the Nth element from a sequence."
:tags["easy" "seqs" "core-functions"]
:tests ["(= (__ '(4 5 6 7) 2) 6)"
"(= (__ [:a :b :c] 0) :a)"
"(= (__ [1 2 3 4] 1) 2)"
"(= (__ '([1 2] [3 4] [5 6]) 2) [5 6])"]})
(insert! :problems
{:_id 22
:title "Count a Sequence"
:times-solved 0
:restricted ["count"]
:description "Write a function which returns the total number of elements in a sequence."
:tags["easy" "seqs" "core-functions"]
:tests ["(= (__ '(1 2 3 3 1)) 5)"
"(= (__ \"Hello World\") 11)"
"(= (__ [[1 2] [3 4] [5 6]]) 3)"
"(= (__ '(13)) 1)"
"(= (__ '(:a :b :c)) 3)"]})
(insert! :problems
{:_id 23
:title "Reverse a Sequence"
:times-solved 0
:restricted ["reverse"]
:description "Write a function which reverses a sequence."
:tags["easy" "seqs" "core-functions"]
:tests ["(= (__ [1 2 3 4 5]) [5 4 3 2 1])"
"(= (__ (sorted-set 5 7 2 7)) '(7 5 2))"
"(= (__ [[1 2][3 4][5 6]]) [[5 6][3 4][1 2]])"]})
(insert! :problems
{:_id 24
:title "Sum It All Up"
:times-solved 0
:description "Write a function which returns the sum of a sequence of numbers."
:tags ["easy" "seqs"]
:tests ["(= (__ [1 2 3]) 6)"
"(= (__ (list 0 -2 5 5)) 8)"
"(= (__ #{4 2 1}) 7)"
"(= (__ '(0 0 -1)) -1)"
"(= (__ '(1 10 3)) 14)"]})
(insert! :problems
{:_id 25
:title "Find the odd numbers"
:times-solved 0
:description "Write a function which returns only the odd numbers from a sequence."
:tags["easy" "seqs"]
:tests ["(= (__ #{1 2 3 4 5}) '(1 3 5))"
"(= (__ [4 2 1 6]) '(1))"
"(= (__ [2 2 4 6]) '())"
"(= (__ [1 1 1 3]) '(1 1 1 3))"]})
(insert! :problems
{:_id 26
:title "Fibonacci Sequence"
:times-solved 0
:description "Write a function which returns the first X fibonacci numbers."
:tags["easy" "Fibonacci" "seqs"]
:tests ["(= (__ 3) '(1 1 2))"
"(= (__ 6) '(1 1 2 3 5 8))"
"(= (__ 8) '(1 1 2 3 5 8 13 21))"]})
(insert! :problems
{:_id 27
:title "Palindrome Detector"
:times-solved 0
:description "Write a function which returns true if the given sequence is a palindrome.<br/><br>
Hint: \"racecar\" does not equal '(\\r \\a \\c \\e \\c \\a \\r)"
:tags["easy" "seqs"]
:tests ["(false? (__ '(1 2 3 4 5)))"
"(true? (__ \"racecar\"))"
"(true? (__ [:foo :bar :foo]))"
"(true? (__ '(1 1 3 3 1 1)))"
"(false? (__ '(:a :b :c)))"]})
(insert! :problems
{:_id 28
:title "Flatten a Sequence"
:times-solved 0
:restricted ["flatten"]
:description "Write a function which flattens a sequence."
:tags["easy" "seqs" "core-functions"]
:tests ["(= (__ '((1 2) 3 [4 [5 6]])) '(1 2 3 4 5 6))"
"(= (__ [\"a\" [\"b\"] \"c\"]) '(\"a\" \"b\" \"c\"))"
"(= (__ '((((:a))))) '(:a))"]})
(insert! :problems
{:_id 29
:title "Get the Caps"
:times-solved 0
:description "Write a function which takes a string and returns a new string containing only the capital letters."
:tags["easy" "strings"]
:tests ["(= (__ \"HeLlO, WoRlD!\") \"HLOWRD\")"
"(empty? (__ \"nothing\"))"
"(= (__ \"$#A(*&987Zf\") \"AZ\")"]})
(insert! :problems
{:_id 30
:title "Compress a Sequence"
:times-solved 0
:description "Write a function which removes consecutive duplicates from a sequence."
:tags ["easy" "seqs"]
:tests ["(= (apply str (__ \"Leeeeeerrroyyy\")) \"Leroy\")"
"(= (__ [1 1 2 3 3 2 2 3]) '(1 2 3 2 3))"
"(= (__ [[1 2] [1 2] [3 4] [1 2]]) '([1 2] [3 4] [1 2]))"]})
(insert! :problems
{:_id 31
:title "Pack a Sequence"
:times-solved 0
:description "Write a function which packs consecutive duplicates into sub-lists."
:tags ["easy" "seqs"]
:tests ["(= (__ [1 1 2 1 1 1 3 3]) '((1 1) (2) (1 1 1) (3 3)))"
"(= (__ [:a :a :b :b :c]) '((:a :a) (:b :b) (:c)))"
"(= (__ [[1 2] [1 2] [3 4]]) '(([1 2] [1 2]) ([3 4])))"]})
(insert! :problems
{:_id 32
:title "Duplicate a Sequence"
:times-solved 0
:description "Write a function which duplicates each element of a sequence."
:tags ["easy" "seqs"]
:tests ["(= (__ [1 2 3]) '(1 1 2 2 3 3))"
"(= (__ [:a :a :b :b]) '(:a :a :a :a :b :b :b :b))"
"(= (__ [[1 2] [3 4]]) '([1 2] [1 2] [3 4] [3 4]))"
"(= (__ [44 33]) [44 44 33 33])"]})
(insert! :problems
{:_id 33
:title "Replicate a Sequence"
:times-solved 0
:description "Write a function which replicates each element of a sequence a variable number of times."
:tags ["easy" "seqs"]
:tests ["(= (__ [1 2 3] 2) '(1 1 2 2 3 3))"
"(= (__ [:a :b] 4) '(:a :a :a :a :b :b :b :b))"
"(= (__ [4 5 6] 1) '(4 5 6))"
"(= (__ [[1 2] [3 4]] 2) '([1 2] [1 2] [3 4] [3 4]))"
"(= (__ [44 33] 2) [44 44 33 33])"]})
(insert! :problems
{:_id 34
:title "Implement range"
:times-solved 0
:restricted ["range"]
:description "Write a function which creates a list of all integers in a given range."
:tags ["easy" "seqs" "core-functions"]
:tests ["(= (__ 1 4) '(1 2 3))"
"(= (__ -2 2) '(-2 -1 0 1))"
"(= (__ 5 8) '(5 6 7))"]})
(insert! :problems
{:_id 35
:title "Local bindings"
:times-solved 0
:description "Clojure lets you give local names to values using the special let-form."
:tags ["elementary" "syntax"]
:tests ["(= __ (let [x 5] (+ 2 x)))"
"(= __ (let [x 3, y 10] (- y x)))"
"(= __ (let [x 21] (let [y 3] (/ x y))))"]})
(insert! :problems
{:_id 36
:title "Let it Be"
:times-solved 0
:description "Can you bind x, y, and z so that these are all true?"
:tags ["elementary" "math" "syntax"]
:tests ["(= 10 (let __ (+ x y)))"
"(= 4 (let __ (+ y z)))"
"(= 1 (let __ z))"]})
(insert! :problems
{:_id 37
:title "Regular Expressions"
:times-solved 0
:description "Regex patterns are supported with a special reader macro."
:tags ["elementary" "regex" "syntax"]
:tests ["(= __ (apply str (re-seq #\"[A-Z]+\" \"bA1B3Ce \")))"]})
(insert! :problems
{:_id 38
:title "Maximum value"
:times-solved 0
:restricted ["max" "max-key"]
:description "Write a function which takes a variable number of parameters and returns the maximum value."
:tags ["easy" "core-functions"]
:tests ["(= (__ 1 8 3 4) 8)"
"(= (__ 30 20) 30)"
"(= (__ 45 67 11) 67)"]})
(insert! :problems
{:_id 39
:title "Interleave Two Seqs"
:times-solved 0
:restricted ["interleave"]
:description "Write a function which takes two sequences and returns the first item from each, then the second item from each, then the third, etc."
:tags ["easy" "seqs" "core-functions"]
:tests ["(= (__ [1 2 3] [:a :b :c]) '(1 :a 2 :b 3 :c))"
"(= (__ [1 2] [3 4 5 6]) '(1 3 2 4))"
"(= (__ [1 2 3 4] [5]) [1 5])"
"(= (__ [30 20] [25 15]) [30 25 20 15])"]})
(insert! :problems
{:_id 40
:title "Interpose a Seq"
:times-solved 0
:restricted ["interpose"]
:description "Write a function which separates the items of a sequence by an arbitrary value."
:tags ["easy" "seqs" "core-functions"]
:tests ["(= (__ 0 [1 2 3]) [1 0 2 0 3])"
"(= (apply str (__ \", \" [\"one\" \"two\" \"three\"])) \"one, two, three\")"
"(= (__ :z [:a :b :c :d]) [:a :z :b :z :c :z :d])"]})
(insert! :problems
{:_id 41
:title "Drop Every Nth Item"
:times-solved 0
:description "Write a function which drops every Nth item from a sequence."
:tags ["easy" "seqs"]
:tests ["(= (__ [1 2 3 4 5 6 7 8] 3) [1 2 4 5 7 8])"
"(= (__ [:a :b :c :d :e :f] 2) [:a :c :e])"
"(= (__ [1 2 3 4 5 6] 4) [1 2 3 5 6])"]})
(insert! :problems
{:_id 42
:title "Factorial Fun"
:times-solved 0
:description "Write a function which calculates factorials."
:tags ["easy" "math"]
:tests ["(= (__ 1) 1)"
"(= (__ 3) 6)"
"(= (__ 5) 120)"
"(= (__ 8) 40320)"]})
(insert! :problems
{:_id 43
:title "Reverse Interleave"
:times-solved 0
:description "Write a function which reverses the interleave process into x number of subsequences."
:tags ["medium" "seqs"]
:tests ["(= (__ [1 2 3 4 5 6] 2) '((1 3 5) (2 4 6)))"
"(= (__ (range 9) 3) '((0 3 6) (1 4 7) (2 5 8)))"
"(= (__ (range 10) 5) '((0 5) (1 6) (2 7) (3 8) (4 9)))"]})
(insert! :problems
{:_id 44
:title "Rotate Sequence"
:times-solved 0
:description "Write a function which can rotate a sequence in either direction."
:tags ["medium" "seqs"]
:tests ["(= (__ 2 [1 2 3 4 5]) '(3 4 5 1 2))"
"(= (__ -2 [1 2 3 4 5]) '(4 5 1 2 3))"
"(= (__ 6 [1 2 3 4 5]) '(2 3 4 5 1))"
"(= (__ 1 '(:a :b :c)) '(:b :c :a))"
"(= (__ -4 '(:a :b :c)) '(:c :a :b))"]})
(insert! :problems
{:_id 45
:title "Intro to Iterate"
:times-solved 0
:description "The iterate function can be used to produce an infinite lazy sequence."
:tags ["easy" "seqs"]
:tests ["(= __ (take 5 (iterate #(+ 3 %) 1)))"]})
(insert! :problems
{:_id 46
:title "Flipping out"
:times-solved 0
:description "Write a higher-order function which flips the order of the arguments of an input function."
:tags ["medium" "higher-order-functions"]
:tests ["(= 3 ((__ nth) 2 [1 2 3 4 5]))"
"(= true ((__ >) 7 8))"
"(= 4 ((__ quot) 2 8))"
"(= [1 2 3] ((__ take) [1 2 3 4 5] 3))"]})
(insert! :problems
{:_id 47
:title "Contain Yourself"
:times-solved 0
:description "The contains? function checks if a KEY is present in a given collection. This often leads beginner clojurians to use it incorrectly with numerically indexed collections like vectors and lists."
:tags ["easy"]
:tests ["(contains? #{4 5 6} __)"
"(contains? [1 1 1 1 1] __)"
"(contains? {4 :a 2 :b} __)"
"(not (contains? '(1 2 4) __))"]})
(insert! :problems
{:_id 48
:title "Intro to some"
:times-solved 0
:description "The some function takes a predicate function and a collection. It returns the first logical true value of (predicate x) where x is an item in the collection."
:tags ["easy"]
:tests ["(= __ (some #{2 7 6} [5 6 7 8]))"
"(= __ (some #(when (even? %) %) [5 6 7 8]))"]})
(insert! :problems
{:_id 49
:title "Split a sequence"
:times-solved 0
:restricted ["split-at"]
:description "Write a function which will split a sequence into two parts."
:tags ["easy" "seqs" "core-functions"]
:tests ["(= (__ 3 [1 2 3 4 5 6]) [[1 2 3] [4 5 6]])"
"(= (__ 1 [:a :b :c :d]) [[:a] [:b :c :d]])"
"(= (__ 2 [[1 2] [3 4] [5 6]]) [[[1 2] [3 4]] [[5 6]]])"]})
(insert! :problems
{:_id 50
:title "Split by Type"
:times-solved 0
:description "Write a function which takes a sequence consisting of items with different types and splits them up into a set of homogeneous sub-sequences. The internal order of each sub-sequence should be maintained, but the sub-sequences themselves can be returned in any order (this is why 'set' is used in the test cases)."
:tags ["medium" "seqs"]
:tests ["(= (set (__ [1 :a 2 :b 3 :c])) #{[1 2 3] [:a :b :c]})"
"(= (set (__ [:a \"foo\" \"bar\" :b])) #{[:a :b] [\"foo\" \"bar\"]})"
"(= (set (__ [[1 2] :a [3 4] 5 6 :b])) #{[[1 2] [3 4]] [:a :b] [5 6]})"]})
(insert! :problems
{:_id 51
:title "Advanced Destructuring"
:times-solved 0
:description "Here is an example of some more sophisticated destructuring."
:tags ["easy" "destructuring"]
:tests ["(= [1 2 [3 4 5] [1 2 3 4 5]] (let [[a b & c :as d] __] [a b c d]))"]})
(insert! :problems
{:_id 52
:title "Intro to Destructuring"
:times-solved 0
:description "Let bindings and function parameter lists support destructuring."
:tags ["easy" "destructuring"]
:tests ["(= [2 4] (let [[a b c d e f g] (range)] __))"]})
(insert! :problems
{:_id 53
:title "Longest Increasing Sub-Seq"
:times-solved 0
:description "Given a vector of integers, find the longest consecutive sub-sequence of increasing numbers. If two sub-sequences have the same length, use the one that occurs first."
:tags ["hard" "seqs"]
:tests ["(= (__ [1 0 1 2 3 0 4 5]) [0 1 2 3])"
"(= (__ [5 6 1 3 2 7]) [5 6])"
"(= (__ [2 3 3 4 5]) [3 4 5])"
"(= (__ [7 6 5 4]) [])"]})
(insert! :problems
{:_id 54
:title "Partition a Sequence"
:times-solved 0
:restricted ["partition" "partition-all"]
:description "Write a function which returns a sequence of lists of x items each. Lists of less than x items should not be returned."
:tags ["medium" "seqs" "core-functions"]
:tests ["(= (__ 3 (range 9)) '((0 1 2) (3 4 5) (6 7 8)))"
"(= (__ 2 (range 8)) '((0 1) (2 3) (4 5) (6 7)))"
"(= (__ 3 (range 8)) '((0 1 2) (3 4 5)))"]})
(insert! :problems
{:_id 55
:title "Count Occurences"
:times-solved 0
:restricted ["frequencies"]
:description "Write a function which returns a map containing the number of occurences of each distinct item in a sequence."
:tags ["medium" "seqs" "core-functions"]
:tests ["(= (__ [1 1 2 3 2 1 1]) {1 4, 2 2, 3 1})"
"(= (__ [:b :a :b :a :b]) {:a 2, :b 3})"
"(= (__ '([1 2] [1 3] [1 3])) {[1 2] 1, [1 3] 2})"]})
(insert! :problems
{:_id 56
:title "Find Distinct Items"
:times-solved 0
:restricted ["distinct"]
:description "Write a function which removes the duplicates from a sequence. Order of the items must be maintained."
:tags ["medium" "seqs" "core-functions"]
:tests ["(= (__ [1 2 1 3 1 2 4]) [1 2 3 4])"
"(= (__ [:a :a :b :b :c :c]) [:a :b :c])"
"(= (__ '([2 4] [1 2] [1 3] [1 3])) '([2 4] [1 2] [1 3]))"]})
(insert! :problems
{:_id 56
:title "Find Distinct Items"
:times-solved 0
:restricted ["distinct"]
:description "Write a function which removes the duplicates from a sequence. Order of the items must be maintained."
:tags ["medium" "seqs" "core-functions"]
:tests ["(= (__ [1 2 1 3 1 2 4]) [1 2 3 4])"
"(= (__ [:a :a :b :b :c :c]) [:a :b :c])"
"(= (__ '([2 4] [1 2] [1 3] [1 3])) '([2 4] [1 2] [1 3]))"
"(= (__ (range 50)) (range 50))"]})
(insert! :problems
{:_id 57
:title "Simple Recursion"
:times-solved 0
:description "A recursive function is a function which calls itself. This is one of the fundamental techniques used in functional programming."
:tags ["elementary" "recursion"]
:tests ["(= __ ((fn foo [x] (when (> x 0) (conj (foo (dec x)) x))) 5))"]})
(insert! :problems
{:_id 58
:title "Function Composition"
:times-solved 0
:restricted ["comp"]
:description "Write a function which allows you to create function compositions. The parameter list should take a variable number of functions, and create a function applies them from right-to-left."
:tags ["medium" "higher-order-functions" "core-functions"]
:tests ["(= [3 2 1] ((__ rest reverse) [1 2 3 4]))"
"(= 5 ((__ (partial + 3) second) [1 2 3 4]))"
"(= true ((__ zero? #(mod % 8) +) 3 5 7 9))"
"(= \"HELLO\" ((__ #(.toUpperCase %) #(apply str %) take) 5 \"hello world\"))"]})
(insert! :problems
{:_id 59
:title "Juxtaposition"
:times-solved 0
:restricted ["juxt"]
:description "Take a set of functions and return a new function that takes a variable number of arguments and returns a sequence containing the result of applying each function left-to-right to the argument list."
:tags ["medium" "higher-order-functions" "core-functions"]
:tests ["(= [21 6 1] ((__ + max min) 2 3 5 1 6 4))"
"(= [\"HELLO\" 5] ((__ #(.toUpperCase %) count) \"hello\"))"
"(= [2 6 4] ((__ :a :c :b) {:a 2, :b 4, :c 6, :d 8 :e 10}))"]})
(insert! :problems
{:_id 60
:title "Sequence Reductions"
:times-solved 0
:restricted ["reductions"]
:description "Write a function which behaves like reduce, but returns each intermediate value of the reduction. Your function must accept either two or three arguments, and the return sequence must be lazy."
:tags ["medium" "seqs" "core-functions"]
:tests ["(= (take 5 (__ + (range))) [0 1 3 6 10])"
"(= (__ conj [1] [2 3 4]) [[1] [1 2] [1 2 3] [1 2 3 4]])"
"(= (last (__ * 2 [3 4 5])) (reduce * 2 [3 4 5]) 120)"]})
(insert! :problems
{:_id 61
:title "Map Construction"
:times-solved 0
:restricted ["zipmap"]
:description "Write a function which takes a vector of keys and a vector of values and constructs a map from them."
:tags ["easy" "core-functions"]
:tests ["(= (__ [:a :b :c] [1 2 3]) {:a 1, :b 2, :c 3})"
"(= (__ [1 2 3 4] [\"one\" \"two\" \"three\"]) {1 \"one\", 2 \"two\", 3 \"three\"})"
"(= (__ [:foo :bar] [\"foo\" \"bar\" \"baz\"]) {:foo \"foo\", :bar \"bar\"})"]})
(insert! :problems
{:_id 62
:title "Re-implement Iteration"
:times-solved 0
:restricted ["iterate"]
:description "Given a side-effect free function f and an initial value x write a function which returns an infinite lazy sequence of x, (f x), (f (f x)), (f (f (f x))), etc."
:tags ["easy" "seqs" "core-functions"]
:tests ["(= (take 5 (__ #(* 2 %) 1)) [1 2 4 8 16])"
"(= (take 100 (__ inc 0)) (take 100 (range)))"
"(= (take 9 (__ #(inc (mod % 3)) 1)) (take 9 (cycle [1 2 3])))"]})
(insert! :problems
{:_id 63
:title "Group a Sequence"
:times-solved 0
:restricted ["group-by"]
:description "Given a function f and a sequence s, write a function which returns a map. The keys should be the values of f applied to each item in s. The value at each key should be a vector of corresponding items in the order they appear in s."
:tags ["medium" "seqs" "core-functions"]
:tests ["(= (__ #(> % 5) #{1 3 6 8}) {false [1 3], true [6 8]})"
"(= (__ #(apply / %) [[1 2] [2 4] [4 6] [3 6]])\n {1/2 [[1 2] [2 4] [3 6]], 2/3 [[4 6]]})"
"(= (__ count [[1] [1 2] [3] [1 2 3] [2 3]])\n {1 [[1] [3]], 2 [[1 2] [2 3]], 3 [[1 2 3]]})"]})
(insert! :problems
{:_id 64
:title "Intro to Reduce"
:times-solved 0
:description "<a href='http://clojuredocs.org/clojure_core/clojure.core/reduce'>Reduce</a> takes a 2 argument function and an optional starting value. It then applies the function to the first 2 items in the sequence (or the starting value and the first element of the sequence). In the next iteration the function will be called on the previous return value and the next item from the sequence, thus reducing the entire collection to one value. Don't worry, it's not as complicated as it sounds."
:tags ["elementary" "seqs"]
:tests ["(= 15 (reduce __ [1 2 3 4 5]))"
"(= 0 (reduce __ []))"
"(= 6 (reduce __ 1 [2 3]))"]})
(insert! :problems
{:_id 65
:title "Black Box Testing"
:times-solved 0
:description "Clojure has many collection types, which act in subtly different ways. The core functions typically convert them into a uniform \"sequence\" type and work with them that way, but it can be important to understand the behavioral and performance differences so that you know which kind is appropriate for your application.<br /><br />Write a function which takes a collection and returns one of :map, :set, :list, or :vector - describing the type of collection it was given.<br />You won't be allowed to inspect their class or use the built-in predicates like list? - the point is to poke at them and understand their behavior."
:tags ["hard" "seqs" "testing"]
:tests ["(= :map (__ {:a 1, :b 2}))",
"(= :list (__ (range (rand-int 20))))",
"(= :vector (__ [1 2 3 4 5 6]))",
"(= :set (__ #{10 (rand-int 5)}))",
"(= [:map :set :vector :list] (map __ [{} #{} [] ()]))"]
:restricted (map str '[class type Class vector? sequential?
list? seq? map? set? instance? getClass])})
(insert! :problems
{:_id 66
:title "Greatest Common Divisor"
:times-solved 0
:description "Given two integers, write a function which
returns the greatest common divisor."
:tags ["easy"]
:tests ["(= (__ 2 4) 2)"
"(= (__ 10 5) 5)"
"(= (__ 5 7) 1)"
"(= (__ 1023 858) 33)"]})
(insert! :problems
{:_id 67
:title "Prime Numbers"
:times-solved 0
:description "Write a function which returns the first x
number of prime numbers."
:tags ["medium" "primes"]
:tests ["(= (__ 2) [2 3])"
"(= (__ 5) [2 3 5 7 11])"
"(= (last (__ 100)) 541)"]})
(insert! :problems
{:_id 68
:title "Power Set"
:times-solved 0
:description "A power set is the set of all subsets of a given set. Given a list, produce a set of sublists while preserving the order of elements."
:tags ["medium" "seqs"]
:tests ["(= (__ '(1 :a)) '#{(1 :a) (:a) () (1)})"
"(= (__ '()) '#{()})"
"(= (__ '(1 2 3)) '#{() (1) (2) (3) (1 2) (1 3) (2 3) (1 2 3)})"
"(= (count (__ (range 10))) 1024)"]})
))
(load-problems)
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