Below is the syntax highlighted version of SequentialSearchST.java.
/****************************************************************************** * Compilation: javac SequentialSearchST.java * Execution: java SequentialSearchST * Dependencies: StdIn.java StdOut.java * Data files: https://algs4.cs.princeton.edu/31elementary/tinyST.txt * * Symbol table implementation with sequential search in an * unordered linked list of key-value pairs. * * % more tinyST.txt * S E A R C H E X A M P L E * * % java SequentialSearchST < tinyST.txt * L 11 * P 10 * M 9 * X 7 * H 5 * C 4 * R 3 * A 8 * E 12 * S 0 * ******************************************************************************/ package edu.princeton.cs.algs4; /** * The {@code SequentialSearchST} class represents an (unordered) * symbol table of generic key-value pairs. * It supports the usual <em>put</em>, <em>get</em>, <em>contains</em>, * <em>delete</em>, <em>size</em>, and <em>is-empty</em> methods. * It also provides a <em>keys</em> method for iterating over all of the keys. * A symbol table implements the <em>associative array</em> abstraction: * when associating a value with a key that is already in the symbol table, * the convention is to replace the old value with the new value. * The class also uses the convention that values cannot be {@code null}. Setting the * value associated with a key to {@code null} is equivalent to deleting the key * from the symbol table. * <p> * It relies on the {@code equals()} method to test whether two keys * are equal. It does not call either the {@code compareTo()} or * {@code hashCode()} method. * <p> * This implementation uses a <em>singly linked list</em> and * <em>sequential search</em>. * The <em>put</em> and <em>delete</em> operations take Θ(<em>n</em>). * The <em>get</em> and <em>contains</em> operations takes Θ(<em>n</em>) * time in the worst case. * The <em>size</em>, and <em>is-empty</em> operations take Θ(1) time. * Construction takes Θ(1) time. * <p> * For additional documentation, see * <a href="https://algs4.cs.princeton.edu/31elementary">Section 3.1</a> of * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne. * * @author Robert Sedgewick * @author Kevin Wayne */ public class SequentialSearchST<Key, Value> { private int n; // number of key-value pairs private Node first; // the linked list of key-value pairs // a helper linked list data type private class Node { private Key key; private Value val; private Node next; public Node(Key key, Value val, Node next) { this.key = key; this.val = val; this.next = next; } } /** * Initializes an empty symbol table. */ public SequentialSearchST() { } /** * Returns the number of key-value pairs in this symbol table. * * @return the number of key-value pairs in this symbol table */ public int size() { return n; } /** * Returns true if this symbol table is empty. * * @return {@code true} if this symbol table is empty; * {@code false} otherwise */ public boolean isEmpty() { return size() == 0; } /** * Returns true if this symbol table contains the specified key. * * @param key the key * @return {@code true} if this symbol table contains {@code key}; * {@code false} otherwise * @throws IllegalArgumentException if {@code key} is {@code null} */ public boolean contains(Key key) { if (key == null) throw new IllegalArgumentException("argument to contains() is null"); return get(key) != null; } /** * Returns the value associated with the given key in this symbol table. * * @param key the key * @return the value associated with the given key if the key is in the symbol table * and {@code null} if the key is not in the symbol table * @throws IllegalArgumentException if {@code key} is {@code null} */ public Value get(Key key) { if (key == null) throw new IllegalArgumentException("argument to get() is null"); for (Node x = first; x != null; x = x.next) { if (key.equals(x.key)) return x.val; } return null; } /** * Inserts the specified key-value pair into the symbol table, overwriting the old * value with the new value if the symbol table already contains the specified key. * Deletes the specified key (and its associated value) from this symbol table * if the specified value is {@code null}. * * @param key the key * @param val the value * @throws IllegalArgumentException if {@code key} is {@code null} */ public void put(Key key, Value val) { if (key == null) throw new IllegalArgumentException("first argument to put() is null"); if (val == null) { delete(key); return; } for (Node x = first; x != null; x = x.next) { if (key.equals(x.key)) { x.val = val; return; } } first = new Node(key, val, first); n++; } /** * Removes the specified key and its associated value from this symbol table * (if the key is in this symbol table). * * @param key the key * @throws IllegalArgumentException if {@code key} is {@code null} */ public void delete(Key key) { if (key == null) throw new IllegalArgumentException("argument to delete() is null"); first = delete(first, key); } // delete key in linked list beginning at Node x // warning: function call stack too large if table is large private Node delete(Node x, Key key) { if (x == null) return null; if (key.equals(x.key)) { n--; return x.next; } x.next = delete(x.next, key); return x; } /** * Returns all keys in the symbol table as an {@code Iterable}. * To iterate over all of the keys in the symbol table named {@code st}, * use the foreach notation: {@code for (Key key : st.keys())}. * * @return all keys in the symbol table */ public Iterable<Key> keys() { Queue<Key> queue = new Queue<Key>(); for (Node x = first; x != null; x = x.next) queue.enqueue(x.key); return queue; } /** * Unit tests the {@code SequentialSearchST} data type. * * @param args the command-line arguments */ public static void main(String[] args) { SequentialSearchST<String, Integer> st = new SequentialSearchST<String, Integer>(); for (int i = 0; !StdIn.isEmpty(); i++) { String key = StdIn.readString(); st.put(key, i); } for (String s : st.keys()) StdOut.println(s + " " + st.get(s)); } } /****************************************************************************** * Copyright 2002-2022, Robert Sedgewick and Kevin Wayne. * * This file is part of algs4.jar, which accompanies the textbook * * Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne, * Addison-Wesley Professional, 2011, ISBN 0-321-57351-X. * http://algs4.cs.princeton.edu * * * algs4.jar is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * algs4.jar is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with algs4.jar. If not, see http://www.gnu.org/licenses. ******************************************************************************/