For this I need to create size, delete and keys. I\'m not sure what information
ID: 3662290 • Letter: F
Question
For this I need to create size, delete and keys. I'm not sure what information I need to include from what I have and all my research hasn't given me much and I'm not getting any output. I need editing help and to point out where I'm going wrong.
My code:
import edu.princeton.cs.algs4.Queue;
import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;
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;
}
}
public SequentialSearchST() {
}
public int size() {
//Part 1
return N;
}
public boolean isEmpty() {
return size() == 0;
}
public boolean contains(Key key) {
if (key == null) throw new NullPointerException("argument to contains() is null");
return get(key) != null;
}
public Value get(Key key) {
if (key == null) throw new NullPointerException("argument to get() is null");
for (Node x = first; x != null; x = x.next) {
if (key.equals(x.key))
return x.val;
}
return null;
}
public void put(Key key, Value val) {
if (key == null) throw new NullPointerException("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++;
}
public void delete(Key key) {
//Part 2?
if (key == null) throw new NullPointerException("argument to delete() is null");
first = delete(first, key);
}
private Node delete(Node x, Key key) {
//or is this Part 2?
if (x == null) return null;
if (key.equals(x.key)) {
N--;
return x.next;
}
x.next = delete(x.next, key);
return x;
}
public Iterable<Key> keys() {
//Part 3
Queue<Key> queue = new Queue<Key>();
for (Node x = first; x != null; x = x.next)
queue.enqueue(x.key);
return queue;
}
public static void main(String[] args) {
SequentialSearchST<String, Integer> st = new SequentialSearchST<String, Integer>();
st.put("one", 1);
st.put("two", 2);
st.put("three", 3);
st.put("four", 4);
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));
}
}
Explanation / Answer
package edu.princeton.cs.algs4;
import edu.princeton.cs.stdlib.StdIn;
import edu.princeton.cs.stdlib.StdOut;
public class SequentialSearchST<Key, Value> {
private int N;
private Node first;
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;
}
}
public int size() {
return N;
}
public boolean isEmpty() {
return size() == 0;
}
public boolean contains(Key key) {
return get(key) != null;
}
public Value get(Key key) {
for (Node x = first; x != null; x = x.next) {
if (key.equals(x.key))
return x.val;
}
return null;
}
public void put(Key key, Value val) {
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++;
}
public void delete(Key key) {
first = delete(first, key);
}
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;
}
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;
}
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));
}
}