A dictionary that is sorted for you lazy people

Author: Coding4Hours

src/main/java/com/thealgorithms/datastructures/dictionary/DictionarySorted

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+package struct;
+
+/**
+ * A clone of a Python dictionary in a Java class that simulates a key-value store using a hash table
+ * implemented from scratch without using standard collections like Map.
+ */
+public class DictionarySort {
+    private static final int SIZE = 10; // Number of buckets
+    private Bucket[] buckets;
+    private SortStrategy sortStrategy = SortStrategy.KEY; // Default sorting strategy
+
+    /**
+     * Enum to represent sorting strategies.
+     */
+    public enum SortStrategy {
+        KEY, VALUE
+    }
+
+    /**
+     * Inner class to represent a key-value pair.
+     */
+    private static class Entry {
+        String key;
+        Object value;
+
+        Entry(String key, Object value) {
+            this.key = key;
+            this.value = value;
+        }
+    }
+
+    /**
+     * Inner class to represent a bucket in the hash table.
+     */
+    private static class Bucket {
+        Entry entry;
+        Bucket next;
+
+        Bucket(Entry entry) {
+            this.entry = entry;
+            this.next = null;
+        }
+    }
+
+    /**
+     * Constructs an empty dictionary.
+     */
+    public DictionarySort() {
+        this.buckets = new Bucket[SIZE];
+    }
+
+    /**
+     * Constructs a dictionary with initial key-value pairs.
+     * 
+     * @param keyValuePairs An even number of arguments where each pair consists of a key and a value.
+     * @throws IllegalArgumentException if the number of arguments is odd.
+     */
+    public DictionarySort(Object... keyValuePairs) {
+        this();
+        if (keyValuePairs.length % 2 != 0) {
+            throw new IllegalArgumentException("Key-value pairs must be even.");
+        }
+        for (int i = 0; i < keyValuePairs.length; i += 2) {
+            String key = (String) keyValuePairs[i];
+            Object value = keyValuePairs[i + 1];
+            put(key, value);
+        }
+    }
+
+    /**
+     * Computes the index in the hash table for a given key.
+     * 
+     * @param key The key for which the index is computed.
+     * @return The index in the hash table.
+     */
+    private int getIndex(String key) {
+        return Math.abs(key.hashCode()) % SIZE;
+    }
+
+    /**
+     * Adds or updates a key-value pair in the dictionary.
+     * 
+     * @param key   The key to be added or updated.
+     * @param value The value associated with the key.
+     */
+    public void put(String key, Object value) {
+        int index = getIndex(key);
+        Bucket bucket = buckets[index];
+
+        // Traverse the bucket to find if the key already exists
+        while (bucket != null) {
+            if (bucket.entry.key.equals(key)) {
+                // Update the value if the key is found
+                bucket.entry.value = value;
+                return;
+            }
+            bucket = bucket.next;
+        }
+
+        // If key is not found, add a new entry to the beginning of the bucket
+        Bucket newBucket = new Bucket(new Entry(key, value));
+        newBucket.next = buckets[index];
+        buckets[index] = newBucket;
+    }
+
+    /**
+     * Retrieves the value associated with a given key.
+     * 
+     * @param key The key whose value is to be retrieved.
+     * @return The value associated with the key, or null if the key is not found.
+     */
+    public Object get(String key) {
+        int index = getIndex(key);
+        Bucket bucket = buckets[index];
+
+        // Traverse the bucket to find the key
+        while (bucket != null) {
+            if (bucket.entry.key.equals(key)) {
+                return bucket.entry.value;
+            }
+            bucket = bucket.next;
+        }
+        return null; // Return null if the key is not found
+    }
+
+    /**
+     * Removes the key-value pair associated with the given key.
+     * 
+     * @param key The key to be removed.
+     */
+    public void remove(String key) {
+        int index = getIndex(key);
+        Bucket bucket = buckets[index];
+        Bucket prev = null;
+
+        // Traverse the bucket to find the key
+        while (bucket != null) {
+            if (bucket.entry.key.equals(key)) {
+                if (prev == null) {
+                    // Removing the first bucket in the slot
+                    buckets[index] = bucket.next;
+                } else {
+                    // Removing a bucket from the middle or end
+                    prev.next = bucket.next;
+                }
+                return;
+            }
+            prev = bucket;
+            bucket = bucket.next;
+        }
+    }
+
+    /**
+     * Checks if the dictionary contains the specified key.
+     * 
+     * @param key The key to check for.
+     * @return true if the dictionary contains the key, false otherwise.
+     */
+    public boolean containsKey(String key) {
+        int index = getIndex(key);
+        Bucket bucket = buckets[index];
+
+        // Traverse the bucket to find the key
+        while (bucket != null) {
+            if (bucket.entry.key.equals(key)) {
+                return true;
+            }
+            bucket = bucket.next;
+        }
+        return false;
+    }
+
+    /**
+     * Sets the sorting strategy for the dictionary.
+     * 
+     * @param strategy The sorting strategy to use.
+     */
+    public void setSortStrategy(SortStrategy strategy) {
+        this.sortStrategy = strategy;
+    }
+
+    /**
+     * Returns a string representation of the dictionary in a JSON-like format without formatting.
+     * 
+     * @return A JSON-like string representation of the dictionary.
+     */
+    @Override
+    public String toString() {
+        return toString(false);
+    }
+
+    /**
+     * Returns a string representation of the dictionary in a JSON-like format with optional formatting.
+     * 
+     * @param formatted If true, returns the string in a formatted JSON-like format.
+     * @return A JSON-like string representation of the dictionary.
+     */
+    public String toString(boolean formatted) {
+        StringBuilder sb = new StringBuilder();
+        sb.append(formatted ? "{\n" : "{");
+
+        Entry[] entries = getAllEntries();
+        if (sortStrategy == SortStrategy.KEY) {
+            sortByKey(entries);
+        } else if (sortStrategy == SortStrategy.VALUE) {
+            sortByValue(entries);
+        }
+
+        boolean first = true;
+        for (Entry entry : entries) {
+            if (!first) {
+                sb.append(formatted ? ",\n" : ", ");
+            }
+            sb.append(formatted ? "  " : "")
+              .append("\"").append(entry.key).append("\": ")
+              .append("\"").append(entry.value.toString()).append("\"");
+            first = false;
+        }
+        sb.append(formatted ? "\n}" : "}");
+        return sb.toString();
+    }
+
+    /**
+     * Retrieves all entries from the dictionary.
+     * 
+     * @return An array of all entries.
+     */
+    private Entry[] getAllEntries() {
+        // Gather all entries from all buckets
+        int count = 0;
+        for (Bucket bucket : buckets) {
+            while (bucket != null) {
+                count++;
+                bucket = bucket.next;
+            }
+        }
+
+        Entry[] entries = new Entry[count];
+        int index = 0;
+        for (Bucket bucket : buckets) {
+            while (bucket != null) {
+                entries[index++] = bucket.entry;
+                bucket = bucket.next;
+            }
+        }
+        return entries;
+    }
+
+    /**
+     * Sorts entries by key using quicksort.
+     * 
+     * @param entries The array of entries to be sorted.
+     */
+    private void sortByKey(Entry[] entries) {
+        quickSort(entries, 0, entries.length - 1, true);
+    }
+
+    /**
+     * Sorts entries by value using quicksort.
+     * 
+     * @param entries The array of entries to be sorted.
+     */
+    private void sortByValue(Entry[] entries) {
+        quickSort(entries, 0, entries.length - 1, false);
+    }
+
+    /**
+     * Quicksort implementation to sort entries by key or value.
+     * 
+     * @param entries The array of entries to be sorted.
+     * @param low     The starting index.
+     * @param high    The ending index.
+     * @param byKey   True to sort by key, false to sort by value.
+     */
+    private void quickSort(Entry[] entries, int low, int high, boolean byKey) {
+        if (low < high) {
+            int pivotIndex = partition(entries, low, high, byKey);
+            quickSort(entries, low, pivotIndex - 1, byKey);
+            quickSort(entries, pivotIndex + 1, high, byKey);
+        }
+    }
+
+    /**
+     * Partition method for quicksort.
+     * 
+     * @param entries The array of entries to be partitioned.
+     * @param low     The starting index.
+     * @param high    The ending index.
+     * @param byKey   True to sort by key, false to sort by value.
+     * @return The index of the pivot element.
+     */
+    private int partition(Entry[] entries, int low, int high, boolean byKey) {
+        Entry pivot = entries[high];
+        int i = low - 1;
+        for (int j = low; j < high; j++) {
+            boolean condition;
+            if (byKey) {
+                condition = entries[j].key.compareTo(pivot.key) < 0;
+            } else {
+                condition = entries[j].value.toString().compareTo(pivot.value.toString()) < 0;
+            }
+            if (condition) {
+                i++;
+                Entry temp = entries[i];
+                entries[i] = entries[j];
+                entries[j] = temp;
+            }
+        }
+        Entry temp = entries[i + 1];
+        entries[i + 1] = entries[high];
+        entries[high] = temp;
+        return i + 1;
+    }
+}