From 8e5d4ea7529ae4f93e56af76e456daac1ed0a30e Mon Sep 17 00:00:00 2001
From: Ivsucram <ivsucram@gmail.com>
Date: Sun, 13 Apr 2025 20:03:59 +0800
Subject: [PATCH] Tutorial 6 - 13 April 2025

---
 T6/Answer/Q1 - count_words.py                 |  85 +++++++++++++
 T6/Answer/Q2 - find_words_with_prefix.py      |  98 +++++++++++++++
 .../Q3 - find_shortest_word_with_prefix.py    | 112 ++++++++++++++++++
 T6/Base/Q1 - count_words.py                   |  75 ++++++++++++
 T6/Base/Q2 - find_words_with_prefix.py        |  83 +++++++++++++
 .../Q3 - find_shortest_word_with_prefix.py    |  80 +++++++++++++
 6 files changed, 533 insertions(+)
 create mode 100644 T6/Answer/Q1 - count_words.py
 create mode 100644 T6/Answer/Q2 - find_words_with_prefix.py
 create mode 100644 T6/Answer/Q3 - find_shortest_word_with_prefix.py
 create mode 100644 T6/Base/Q1 - count_words.py
 create mode 100644 T6/Base/Q2 - find_words_with_prefix.py
 create mode 100644 T6/Base/Q3 - find_shortest_word_with_prefix.py

diff --git a/T6/Answer/Q1 - count_words.py b/T6/Answer/Q1 - count_words.py
new file mode 100644
index 0000000..26aef07
--- /dev/null
+++ b/T6/Answer/Q1 - count_words.py	
@@ -0,0 +1,85 @@
+class TrieNode:
+    def __init__(self, char=None):
+        self.char = char
+        self.first_child = None
+        self.next_sibling = None
+        self.is_end_of_word = False
+
+class Queue:
+    def __init__(self):
+        self.items = []
+
+    def enqueue(self, item):
+        self.items.append(item)  # Add to the end
+
+    def dequeue(self):
+        if not self.is_empty():
+            return self.items.pop(0)  # Remove from the front
+        return None
+
+    def is_empty(self):
+        return len(self.items) == 0
+
+    def size(self):
+        return len(self.items)
+
+def _find_child(node, char):
+    current = node.first_child
+    while current:
+        if current.char == char:
+            return current
+        current = current.next_sibling
+    return None
+
+
+def _add_child(node, char):
+    new_node = TrieNode(char)
+    new_node.next_sibling = node.first_child
+    node.first_child = new_node
+    return new_node
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+
+    def insert(self, word):
+        node = self.root
+        for char in word:
+            child = _find_child(node, char)
+            if not child:
+                child = _add_child(node, char)
+            node = child
+        node.is_end_of_word = True
+
+    def search(self, word):
+        node = self.root
+        for char in word:
+            node = _find_child(node, char)
+            if not node:
+                return False
+        return node.is_end_of_word
+
+    def count_words(self, node): #question 1
+        if node.is_end_of_word:
+            cnt = 1
+        else:
+            cnt = 0
+
+        child = node.first_child
+        while child:
+            cnt += self.count_words(child)
+            child = child.next_sibling
+        return cnt
+
+trie = Trie()
+trie.insert("cat")
+trie.insert("car")
+trie.insert("care")
+trie.insert("cane")
+trie.insert("camera")
+trie.insert("campus")
+trie.insert("camp")
+trie.insert("dog")
+trie.insert("dot")
+
+print("Total words in Trie:", trie.count_words(trie.root))
\ No newline at end of file
diff --git a/T6/Answer/Q2 - find_words_with_prefix.py b/T6/Answer/Q2 - find_words_with_prefix.py
new file mode 100644
index 0000000..887ea89
--- /dev/null
+++ b/T6/Answer/Q2 - find_words_with_prefix.py	
@@ -0,0 +1,98 @@
+class TrieNode:
+    def __init__(self, char=None):
+        self.char = char
+        self.first_child = None
+        self.next_sibling = None
+        self.is_end_of_word = False
+
+class Queue:
+    def __init__(self):
+        self.items = []
+
+    def enqueue(self, item):
+        self.items.append(item)  # Add to the end
+
+    def dequeue(self):
+        if not self.is_empty():
+            return self.items.pop(0)  # Remove from the front
+        return None
+
+    def is_empty(self):
+        return len(self.items) == 0
+
+    def size(self):
+        return len(self.items)
+
+def _find_child(node, char):
+    current = node.first_child
+    while current:
+        if current.char == char:
+            return current
+        current = current.next_sibling
+    return None
+
+def _add_child(node, char):
+    new_node = TrieNode(char)
+    new_node.next_sibling = node.first_child
+    node.first_child = new_node
+    return new_node
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+
+    def insert(self, word):
+        node = self.root
+        for char in word:
+            child = _find_child(node, char)
+            if not child:
+                child = _add_child(node, char)
+            node = child
+        node.is_end_of_word = True
+
+    def search(self, word):
+        node = self.root
+        for char in word:
+            node = _find_child(node, char)
+            if not node:
+                return False
+        return node.is_end_of_word
+
+    def collect_all_words(self, node, prefix, results):
+        if node.is_end_of_word:
+            results.append(prefix)
+
+        child = node.first_child
+        while child:
+            self.collect_all_words(child, prefix + child.char, results)
+            child = child.next_sibling
+
+    def find_words_with_prefix(self, prefix): #question 2
+        results = []
+        node = self.root
+
+        for char in prefix:
+            node = _find_child(node, char)
+            if not node:
+                return []
+
+        self.collect_all_words(node, prefix, results)
+        return results
+
+trie = Trie()
+trie.insert("cat")
+trie.insert("car")
+trie.insert("care")
+trie.insert("cane")
+trie.insert("camera")
+trie.insert("campus")
+trie.insert("camp")
+trie.insert("dog")
+trie.insert("dot")
+
+prefix1 = "ca"
+prefix2 = "do"
+prefix3 = "z"
+print(f"Words starting with '{prefix1}': ", trie.find_words_with_prefix(prefix1))
+print(f"Words starting with '{prefix2}':", trie.find_words_with_prefix(prefix2))
+print(f"Words starting with '{prefix3}':", trie.find_words_with_prefix(prefix3))
\ No newline at end of file
diff --git a/T6/Answer/Q3 - find_shortest_word_with_prefix.py b/T6/Answer/Q3 - find_shortest_word_with_prefix.py
new file mode 100644
index 0000000..5aa47b3
--- /dev/null
+++ b/T6/Answer/Q3 - find_shortest_word_with_prefix.py	
@@ -0,0 +1,112 @@
+class TrieNode:
+    def __init__(self, char=None):
+        self.char = char
+        self.first_child = None
+        self.next_sibling = None
+        self.is_end_of_word = False
+
+class Queue:
+    def __init__(self):
+        self.items = []
+
+    def enqueue(self, item):
+        self.items.append(item)  # Add to the end
+
+    def dequeue(self):
+        if not self.is_empty():
+            return self.items.pop(0)  # Remove from the front
+        return None
+
+    def is_empty(self):
+        return len(self.items) == 0
+
+    def size(self):
+        return len(self.items)
+
+def _find_child(node, char):
+    current = node.first_child
+    while current:
+        if current.char == char:
+            return current
+        current = current.next_sibling
+    return None
+
+def _add_child(node, char):
+    new_node = TrieNode(char)
+    new_node.next_sibling = node.first_child
+    node.first_child = new_node
+    return new_node
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+
+    def insert(self, word):
+        node = self.root
+        for char in word:
+            child = _find_child(node, char)
+            if not child:
+                child = _add_child(node, char)
+            node = child
+        node.is_end_of_word = True
+
+    def search(self, word):
+        node = self.root
+        for char in word:
+            node = _find_child(node, char)
+            if not node:
+                return False
+        return node.is_end_of_word
+
+    def find_shortest_word_with_prefix(self, prefix):#question 3
+        # Step 1: Traverse to the end of the prefix
+        node = self.root
+        for char in prefix:
+            node = _find_child(node, char)
+            if not node:
+                return None  # Prefix not found
+
+        # Step 2: BFS
+        queue = Queue()
+        queue.enqueue((node, prefix, 0))  # (node, word, depth)
+        shortest_words = []
+        min_depth = None
+
+        while not queue.is_empty():
+            node, word, depth = queue.dequeue()
+
+            if node.is_end_of_word:
+                if min_depth is None:
+                    min_depth = depth
+                if depth == min_depth:
+                    shortest_words.append(word)
+                elif depth > min_depth:
+                    break  # We already found the shortest level, skip deeper
+
+            if min_depth is not None and depth >= min_depth:
+                continue  # don't enqueue deeper nodes
+
+            child = node.first_child
+            while child:
+                queue.enqueue((child, word + child.char, depth + 1))
+                child = child.next_sibling
+
+        return shortest_words
+
+trie = Trie()
+trie.insert("cat")
+trie.insert("car")
+trie.insert("care")
+trie.insert("cane")
+trie.insert("camera")
+trie.insert("campus")
+trie.insert("camp")
+trie.insert("dog")
+trie.insert("dot")
+
+prefix1 = "ca"
+prefix2 = "do"
+prefix3 = "z"
+print(f"Shortest word starting with '{prefix1}':", trie.find_shortest_word_with_prefix(prefix1))
+print(f"Shortest word starting with '{prefix2}':", trie.find_shortest_word_with_prefix(prefix2))
+print(f"Shortest word starting with '{prefix3}':", trie.find_shortest_word_with_prefix(prefix3))
diff --git a/T6/Base/Q1 - count_words.py b/T6/Base/Q1 - count_words.py
new file mode 100644
index 0000000..a379052
--- /dev/null
+++ b/T6/Base/Q1 - count_words.py	
@@ -0,0 +1,75 @@
+class TrieNode:
+    def __init__(self, char=None):
+        self.char = char
+        self.first_child = None
+        self.next_sibling = None
+        self.is_end_of_word = False
+
+class Queue:
+    def __init__(self):
+        self.items = []
+
+    def enqueue(self, item):
+        self.items.append(item)  # Add to the end
+
+    def dequeue(self):
+        if not self.is_empty():
+            return self.items.pop(0)  # Remove from the front
+        return None
+
+    def is_empty(self):
+        return len(self.items) == 0
+
+    def size(self):
+        return len(self.items)
+
+def _find_child(node, char):
+    current = node.first_child
+    while current:
+        if current.char == char:
+            return current
+        current = current.next_sibling
+    return None
+
+def _add_child(node, char):
+    new_node = TrieNode(char)
+    new_node.next_sibling = node.first_child
+    node.first_child = new_node
+    return new_node
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+
+    def insert(self, word):
+        node = self.root
+        for char in word:
+            child = _find_child(node, char)
+            if not child:
+                child = _add_child(node, char)
+            node = child
+        node.is_end_of_word = True
+
+    def search(self, word):
+        node = self.root
+        for char in word:
+            node = _find_child(node, char)
+            if not node:
+                return False
+        return node.is_end_of_word
+
+    def count_words(self, node): #question 1
+        raise NotImplementedError
+
+trie = Trie()
+trie.insert("cat")
+trie.insert("car")
+trie.insert("care")
+trie.insert("cane")
+trie.insert("camera")
+trie.insert("campus")
+trie.insert("camp")
+trie.insert("dog")
+trie.insert("dot")
+
+print("Total words in Trie:", trie.count_words(trie.root))
\ No newline at end of file
diff --git a/T6/Base/Q2 - find_words_with_prefix.py b/T6/Base/Q2 - find_words_with_prefix.py
new file mode 100644
index 0000000..41bac45
--- /dev/null
+++ b/T6/Base/Q2 - find_words_with_prefix.py	
@@ -0,0 +1,83 @@
+class TrieNode:
+    def __init__(self, char=None):
+        self.char = char
+        self.first_child = None
+        self.next_sibling = None
+        self.is_end_of_word = False
+
+class Queue:
+    def __init__(self):
+        self.items = []
+
+    def enqueue(self, item):
+        self.items.append(item)  # Add to the end
+
+    def dequeue(self):
+        if not self.is_empty():
+            return self.items.pop(0)  # Remove from the front
+        return None
+
+    def is_empty(self):
+        return len(self.items) == 0
+
+    def size(self):
+        return len(self.items)
+
+def _find_child(node, char):
+    current = node.first_child
+    while current:
+        if current.char == char:
+            return current
+        current = current.next_sibling
+    return None
+
+def _add_child(node, char):
+    new_node = TrieNode(char)
+    new_node.next_sibling = node.first_child
+    node.first_child = new_node
+    return new_node
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+
+    def insert(self, word):
+        node = self.root
+        for char in word:
+            child = _find_child(node, char)
+            if not child:
+                child = _add_child(node, char)
+            node = child
+        node.is_end_of_word = True
+
+    def search(self, word):
+        node = self.root
+        for char in word:
+            node = _find_child(node, char)
+            if not node:
+                return False
+        return node.is_end_of_word
+
+    def collect_all_words(self, node, prefix, results):
+        raise NotImplementedError
+
+    def find_words_with_prefix(self, prefix): #question 2
+        raise NotImplementedError
+
+trie = Trie()
+trie.insert("cat")
+trie.insert("car")
+trie.insert("care")
+trie.insert("cane")
+trie.insert("camera")
+trie.insert("campus")
+trie.insert("camp")
+trie.insert("dog")
+trie.insert("dot")
+
+prefix1 = "ca"
+prefix2 = "do"
+prefix3 = "z"
+print(f"Words starting with '{prefix1}': ", trie.find_words_with_prefix(prefix1))
+print(f"Words starting with '{prefix2}':", trie.find_words_with_prefix(prefix2))
+print(f"Words starting with '{prefix3}':", trie.find_words_with_prefix(prefix3))
\ No newline at end of file
diff --git a/T6/Base/Q3 - find_shortest_word_with_prefix.py b/T6/Base/Q3 - find_shortest_word_with_prefix.py
new file mode 100644
index 0000000..863b375
--- /dev/null
+++ b/T6/Base/Q3 - find_shortest_word_with_prefix.py	
@@ -0,0 +1,80 @@
+class TrieNode:
+    def __init__(self, char=None):
+        self.char = char
+        self.first_child = None
+        self.next_sibling = None
+        self.is_end_of_word = False
+
+class Queue:
+    def __init__(self):
+        self.items = []
+
+    def enqueue(self, item):
+        self.items.append(item)  # Add to the end
+
+    def dequeue(self):
+        if not self.is_empty():
+            return self.items.pop(0)  # Remove from the front
+        return None
+
+    def is_empty(self):
+        return len(self.items) == 0
+
+    def size(self):
+        return len(self.items)
+
+def _find_child(node, char):
+    current = node.first_child
+    while current:
+        if current.char == char:
+            return current
+        current = current.next_sibling
+    return None
+
+def _add_child(node, char):
+    new_node = TrieNode(char)
+    new_node.next_sibling = node.first_child
+    node.first_child = new_node
+    return new_node
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+
+    def insert(self, word):
+        node = self.root
+        for char in word:
+            child = _find_child(node, char)
+            if not child:
+                child = _add_child(node, char)
+            node = child
+        node.is_end_of_word = True
+
+    def search(self, word):
+        node = self.root
+        for char in word:
+            node = _find_child(node, char)
+            if not node:
+                return False
+        return node.is_end_of_word
+
+    def find_shortest_word_with_prefix(self, prefix):#question 3
+        raise NotImplementedError
+
+trie = Trie()
+trie.insert("cat")
+trie.insert("car")
+trie.insert("care")
+trie.insert("cane")
+trie.insert("camera")
+trie.insert("campus")
+trie.insert("camp")
+trie.insert("dog")
+trie.insert("dot")
+
+prefix1 = "ca"
+prefix2 = "do"
+prefix3 = "z"
+print(f"Shortest word starting with '{prefix1}':", trie.find_shortest_word_with_prefix(prefix1))
+print(f"Shortest word starting with '{prefix2}':", trie.find_shortest_word_with_prefix(prefix2))
+print(f"Shortest word starting with '{prefix3}':", trie.find_shortest_word_with_prefix(prefix3))