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import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 *
 * Add VM option -ea to enable assertion.
 * 
 * @author Lim, Teck Hooi
 *

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// Ruby

[-15,10,4,-3,5,-7,1,-5].reduce([[]]) {|ll, l| ll + ll.map{|a| a + [l]}}.select{|l| l.inject(:+) == 0}

// (Scala (functions)

List(-15,10,4,-3,5,-7,1,-5).foldLeft(List(List[Int]())){ (ll,l) => ll ++ ll.map{l :: _}}.filter(!_.isEmpty).filter(_.sum == 0)

// Scala (recursion)

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// returns a lazy sequence

def fillAndArrange(xs: Seq[Int], ys: Seq[Int] = 1 to 9): Stream[Seq[Int]] = ys.diff(xs) match {
  case Seq() => Stream(xs)
  case zs => zs.flatten(z => fillAndArrange(xs.updated(xs.indexOf(0),z),zs)).toStream
}

assert(fillAndArrange(List(0, 0, 1, 5, 0, 0, 8, 0, 0)).size == 720)

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trait Monoid[A] {
  def append(a1: A, a2: A): A
  def empty: A
}

object Monoid {
  implicit def ListMonoid[A]: Monoid[List[A]] = new Monoid[List[A]] {
    def append(a1: List[A], a2: List[A]) = a1 ::: a2
    def empty = Nil
  }

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(defn sumAll [x]
  (if (= x 1)
    1
    (+ x (sumAll (dec x)))
  ))

(defn accSumAll [x]
  ((fn [y acc]
  (if (zero? y)
    acc

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val sampleInts = List(1,2,3,4)
val sampleStrings = List("AA", "BB", "CC")

import annotation.implicitNotFound
@implicitNotFound("Member of type class ${T} not found.")
trait Joinable[T] {
  def join(l: List[T]): T
}

implicit object JoinStrings extends Joinable[String] {

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import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;

public class RunMe {

    public static void main(String[] args) {
        List<String> sentences = new ArrayList<String>();

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package org.teckhooi

import java.util.concurrent.{Executors, ThreadFactory}
import java.util.concurrent.atomic.AtomicInteger

import cats.effect.{ExitCode, IO, IOApp}

import scala.concurrent.{ExecutionContext, ExecutionContextExecutor}
import cats.effect._
import cats.implicits._

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package com.test.sample;

import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;

public class FindZeroSumCombi {
	public static void main(String[] args) {

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/**
 * To be a valid value class, the following rules must be followed (taken from Programming Scala 2nd Ed.):
 * 1. The value class has one and only one public val argument (as of Scala 2.11, 
 *    the argument can also be nonpublic).
 * 2. The type of the argument must not be a value class itself.
 * 3. If the value class is parameterized, the @specialized annotation can’t be used.
 * 4. The value class doesn’t define secondary constructors.
 * 5. The value class defines only methods, but no other vals and no vars.
 * 6. However, the value class can’t override equals and hashCode.
 * 7. The value class defines no nested traits, classes, or objects.