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6.170 Recitation: Announcements, Problem Set 3, and Quiz 1 Details

This document outlines important announcements for course 6.170, specifically regarding Problem Set 3 due on March 4, and Quiz 1 review scheduled for March 3 at 7:30 PM in room 34-101. Additionally, Quiz 1 covering lecture notes L1-L10 will take place on March 6 during class. Guidelines for usernames are provided, and it includes details on aspects of problem sets such as Object Models, subtype relationships, multiplicity, and mutability. For further assistance, students are encouraged to visit during office hours or reach out via email.

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6.170 Recitation: Announcements, Problem Set 3, and Quiz 1 Details

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  1. 6.170 Recitation Godfrey Tan

  2. Announcements • Problem Set 3: March 4 • Quiz 1 Review: March 3, 7:30pm, 34-101 • Quiz 1 (L1-L10): March 6 during class • 54-100 for usernames a*-j* • 34-101 for usernames k*-z* • http://web.mit.edu/6.170/www/ • Section number & TA’s name on problem set submissions

  3. Problem 5: MDD

  4. Object Models Describe relationships between objects • Subtype • Multiplicity • Mutability

  5. Subtype Relationship subtype (pure) exhaustive exclusive (disjoint)

  6. Multiplicity • Uses field arrow: • M to N relationship: m, n, *, !, ?, +

  7. Mutability • Modifiability of fields: | • At the src • At the target • Modifiability of sets • Cardinality: +, *, !, ? • Migration: dynamic, static, fixed

  8. Women OM Example: Sets People Men Monk Player Nice Guy

  9. OM Example: Relationships People Men Women + ! ? Monk Player Nice Guy girlfriends ! girlfriends

  10. OM Example: Blasphemy People Men Women + ! + ? Monk Player Nice Guy girlfriends + ! girlfriends girlfriends

  11. Problem 1: CardValue and CardSuit Static members in CardSuit. Separate CardSuit class. CardSuit constructor: if (this == null) … CardValue & CardSuit constructors private CardValue.equals() CardValue implements the Comparable interface

  12. Problem 2: Card public int compareTo(Object o) { if (o == null) throw new NullPointerException(); if (!(o instanceOf Card)) throw new ClassCastException(); Card c = (Card)o; int suitCompare = getSuit().compareTo(c.getSuit()); if (suitCompare != 0) return suitCompare; return getValue().compareTo(c.getValue()); }

  13. Problem 2: Card public boolean equals(Object otherCardObject) { if (!(otherCardObject instanceof Card)) return false; Card otherCard = (Card)otherCardObject; (1) return (value == otherCard.value) && (suit == otherCard.suit); (2) return (this.compareTo(otherCard) == 0); (3) return this.hashCode() == otherCard.hashCode(); }

  14. Problem 3: Deck public Deck() { cards = new ArrayList(52); for (int i=0; i<4; i++) for (int j=0; j<13; j++) cards.add(new Card( (CardValue)(CardValue.VALUES.get(j)), (CardSuit) (CardSuit.SUITS.get(i)))); } CardValue.VALUES.size() instead of 13 CardSuit.SUITS.size() instead of 4

  15. Problem 3: Deck public void removeCard(Card c) { cards.remove(c); } public void removeCard(Card c) { if ((c == null) || !cards.contains(c)) return; cards.remove(c); } ------------------------------------------------------------------------------ public void shuffle() { Collections.shuffle(cards); }

  16. Problem 4: TwoPair public static PokerRanking evaluateHand(Hand h) { if (!validHand(h)) return null; Iterator it = h.listCardsAcesHigh(); SortedSet pairs = PokerRanking.findNOfAKinds(it, 2); if (isValidHand(h) && pairs.size() == 2) { Card pair1 = (Card)pairs.first(); Card pair2 = (Card)pairs.last(); removeNCardsWithValue(it, 2, pair1.getValue()); removeNCardsWithValue(it, 2, pair2.getValue()); SortedSet discard = findNOfAKinds(it, 1); return new TwoPair(pair1, pair2, discard); } else return null; }

  17. Problem 4: TwoPair public static PokerRanking evaluateHand(Hand h) { if (!isValidHand(h)) return null; SortedSet pairsSet = findNOfAKinds(h.listCardsAcesHigh(), 2); if ((pairsSet.isEmpty()) || (pairsSet.size() < 2)) return null; Card firstPair = (Card) pairsSet.first(); Card secondPair = (Card) pairsSet.last(); SortedSet discardableCards = convertToSortedSet(h.listCardsAcesHigh()); removeNCardsWithValue(discardableCards.iterator(), 2, firstPair.getValue()); removeNCardsWithValue(discardableCards.iterator(), 2, secondPair.getValue()); return TwoPair(firstPair, secondPair, discardableCards); }

  18. instanceof v.s. getClass ClassB extends ClassA ClassA a = new ClassA() ClassB b = new ClassB() ClassA ab = new ClassB() a instaneof ClassA b instanceof ClassA a.getClass().equals(b.getClass()) ab instanceof ClassA; ab instanceof ClassB

  19. Designing a Graph ADT What is an ADT? An ADT includes a data structure and a collection of methods which operate on that data structure. • Think of what a graph really is. • What are they used for? • What functionality to provide? Too much; too little • Simplicity: easy to use? • Flexibility: easy to upgrade; easy to maintain? • Implementation Efficiency: easy to implement? • Performance: better to use Sets, Lists, Maps, arrays, etc.? • Familiarize with APIs; think before you code. • Visit me in office hours or send email.

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