Question: Write a java program called ComputeARR to compute the average rating a restaurant is currently getting. The ratings are single-word adjectives, listed in the table
Write a java program called ComputeARR to compute the average rating a restaurant is currently getting. The ratings are single-word adjectives, listed in the table below, along with numeric scores for each. Write the program so that it:
Declares and creates a symbol table using the algs31.BinarySearchST class;
Fills that symbol table with the following rating/score pairings, where the rating is the symbol table key and the score is the symbol table value:
| Key (Rating) | Value (Score) |
|---|---|
| Outstanding | 6 |
| Excellent | 5 |
| Better | 4 |
| Average | 3 |
| Worse | 2 |
| Awful | 1 |
| Avoid | 0 |
Reads a sequence of rating strings from a file called a1ratings.txt (must be created) using StdIn where the ratings are separated from each other by one or more whitespace characters. Read that file by directing StdIn to the file with the fromFile method and then use the method StdIn.readAllStrings() to return an array containing all of the Strings.
Iterates through the array just filled using a for-each loop and accumulates a total score based on the ratings. For each rating, look up its value in the symbol table and add it to the accumulator variable.
Computes and prints the average value as a floating point number. For example, assume the ratings read in are Excellent, Average, Excellent, Better. These yields the scores 5, 3, 5, 4. Averaged this is 4.25.
Create your own test file called a1ratings.txt and place it in the data directory. Remember that your program will open it using the pathname data/a1grades.txt.
algs31.BinarySearchST class
package algs31;
import stdlib.*;
import algs13.Queue;
/* ***********************************************************************
* Compilation: javac BinarySearchST.java
* Execution: java BinarySearchST
* Dependencies: StdIn.java StdOut.java
* Data files: http://algs4.cs.princeton.edu/31elementary/tinyST.txt
*
* Symbol table implementation with binary search in an ordered array.
*
* % more tinyST.txt
* S E A R C H E X A M P L E
*
* % java BinarySearchST < tinyST.txt
* A 8
* C 4
* E 12
* H 5
* L 11
* M 9
* P 10
* R 3
* S 0
* X 7
*
*************************************************************************/
public class BinarySearchST
private static final int INIT_CAPACITY = 2;
private K[] keys;
private V[] vals;
private int N = 0;
// create an empty symbol table with default initial capacity
public BinarySearchST() { this(INIT_CAPACITY); }
// create an empty symbol table with given initial capacity
@SuppressWarnings("unchecked")
public BinarySearchST(int capacity) {
keys = (K[]) new Comparable[capacity];
vals = (V[]) new Object[capacity];
}
// resize the underlying arrays
@SuppressWarnings("unchecked")
private void resize(int capacity) {
if (capacity <= N) throw new IllegalArgumentException ();
K[] tempk = (K[]) new Comparable[capacity];
V[] tempv = (V[]) new Object[capacity];
for (int i = 0; i < N; i++) {
tempk[i] = keys[i];
tempv[i] = vals[i];
}
vals = tempv;
keys = tempk;
}
// is the key in the table?
public boolean contains(K key) { return get(key) != null; }
// number of key-value pairs in the table
public int size() { return N; }
// is the symbol table empty?
public boolean isEmpty() { return size() == 0; }
// return the value associated with the given key, or null if no such key
public V get(K key) {
if (isEmpty()) return null;
int i = rank(key);
if (i < N && keys[i].compareTo(key) == 0) return vals[i];
return null;
}
// return the number of keys in the table that are smaller than given key
public int rank(K key) {
int lo = 0, hi = N-1;
while (lo <= hi) {
int m = lo + (hi - lo) / 2;
int cmp = key.compareTo(keys[m]);
if (cmp < 0) hi = m - 1;
else if (cmp > 0) lo = m + 1;
else return m;
}
return lo;
}
// Search for key. Update value if found; grow table if new.
public void put(K key, V val) {
if (val == null) { delete(key); return; }
int i = rank(key);
// key is already in table
if (i < N && keys[i].compareTo(key) == 0) {
vals[i] = val;
return;
}
// insert new key-value pair
if (N == keys.length) resize(2*keys.length);
for (int j = N; j > i; j--) {
keys[j] = keys[j-1];
vals[j] = vals[j-1];
}
keys[i] = key;
vals[i] = val;
N++;
//assert check();
}
// Remove the key-value pair if present
public void delete(K key) {
if (isEmpty()) return;
// compute rank
int i = rank(key);
// key not in table
if (i == N || keys[i].compareTo(key) != 0) {
return;
}
for (int j = i; j < N-1; j++) {
keys[j] = keys[j+1];
vals[j] = vals[j+1];
}
N--;
keys[N] = null; // to avoid loitering
vals[N] = null;
// resize if 1/4 full
if (N > 0 && N == keys.length/4) resize(keys.length/2);
//assert check();
}
// delete the minimum key and its associated value
public void deleteMin() {
if (isEmpty()) throw new Error("Symbol table underflow error");
delete(min());
}
// delete the maximum key and its associated value
public void deleteMax() {
if (isEmpty()) throw new Error("Symbol table underflow error");
delete(max());
}
/* ***************************************************************************
* Ordered symbol table methods
*****************************************************************************/
public K min() {
if (isEmpty()) return null;
return keys[0];
}
public K max() {
if (isEmpty()) return null;
return keys[N-1];
}
public K select(int k) {
if (k < 0 || k >= N) return null;
return keys[k];
}
public K floor(K key) {
int i = rank(key);
if (i < N && key.compareTo(keys[i]) == 0) return keys[i];
if (i == 0) return null;
else return keys[i-1];
}
public K ceiling(K key) {
int i = rank(key);
if (i == N) return null;
else return keys[i];
}
public int size(K lo, K hi) {
if (lo.compareTo(hi) > 0) return 0;
if (contains(hi)) return rank(hi) - rank(lo) + 1;
else return rank(hi) - rank(lo);
}
public Iterable
return keys(min(), max());
}
public Iterable
Queue
if (lo == null && hi == null) return queue;
if (lo == null) throw new Error("lo is null in keys()");
if (hi == null) throw new Error("hi is null in keys()");
if (lo.compareTo(hi) > 0) return queue;
for (int i = rank(lo); i < rank(hi); i++)
queue.enqueue(keys[i]);
if (contains(hi)) queue.enqueue(keys[rank(hi)]);
return queue;
}
/* ***************************************************************************
* Check internal invariants
*****************************************************************************/
private boolean check() {
return isSorted() && rankCheck();
}
// are the items in the array in ascending order?
private boolean isSorted() {
for (int i = 1; i < size(); i++)
if (keys[i].compareTo(keys[i-1]) < 0) return false;
return true;
}
// check that rank(select(i)) = i
private boolean rankCheck() {
for (int i = 0; i < size(); i++)
if (i != rank(select(i))) return false;
for (int i = 0; i < size(); i++)
if (keys[i].compareTo(select(rank(keys[i]))) != 0) return false;
return true;
}
/* ***************************************************************************
* Test client
*****************************************************************************/
public static void main(String[] args) {
StdIn.fromFile("data/tiny.txt");
BinarySearchST
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));
}
}
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