## Thursday, August 11, 2016

### Print all words matching a pattern in CamelCase Notation Dictonary - GeeksforGeeks

Print all words matching a pattern in CamelCase Notation Dictonary - GeeksforGeeks
Given a dictionary of words where each word follows CamelCase notation, print all words in the dictionary that match with a given pattern consisting of uppercase characters only.

The idea is to insert all dictionary keys into the Trie one by one. Here key refers to only Uppercase characters in original word in CamelCase notation. If we encounter the key for the first time, we need to mark the last node as leaf node and insert the complete word for that key into the vector associated with the leaf node. If we encounter a key that is already in the trie, we update the vector associated with the leaf node with current word. After all dictionary words are processed, we search for the pattern in the trie and print all words that matches the pattern.

`// Alphabet size (# of upper-Case characters)`
`#define ALPHABET_SIZE 26`

`// A Trie node`
`struct` `TrieNode`
`{`
`    ``TrieNode* children[ALPHABET_SIZE];`

`    ``// isLeaf is true if the node represents`
`    ``// end of a word`
`    ``bool` `isLeaf;`

`    ``// vector to store list of complete words`
`    ``// in leaf node`
`    ``list<string> word;`
`};`

`// Returns new Trie node (initialized to NULLs)`
`TrieNode* getNewTrieNode(``void``)`
`{`
`    ``TrieNode* pNode = ``new` `TrieNode;`

`    ``if` `(pNode)`
`    ``{`
`        ``pNode->isLeaf = ``false``;`

`        ``for` `(``int` `i = 0; i < ALPHABET_SIZE; i++)`
`            ``pNode->children[i] = NULL;`
`    ``}`

`    ``return` `pNode;`
`}`

`// Function to insert word into the Trie`
`void` `insert(TrieNode* root, string word)`
`{`
`    ``int` `index;`
`    ``TrieNode* pCrawl = root;`

`    ``for` `(``int` `level = 0; level < word.length(); level++)`
`    ``{`
`        ``// consider only uppercase characters`
`        ``if` `(``islower``(word[level]))`
`            ``continue``;`

`        ``// get current character position`
`        ``index = ``int``(word[level]) - ``'A'``;`
`        ``if` `(!pCrawl->children[index])`
`            ``pCrawl->children[index] = getNewTrieNode();`

`        ``pCrawl = pCrawl->children[index];`
`    ``}`

`    ``// mark last node as leaf`
`    ``pCrawl->isLeaf = ``true``;`

`    ``// push word into vector associated with leaf node`
`    ``(pCrawl->word).push_back(word);`
`}`

`// Function to print all children of Trie node root`
`void` `printAllWords(TrieNode* root)`
`{`
`    ``// if current node is leaf`
`    ``if` `(root->isLeaf)`
`    ``{`
`        ``for``(string str : root->word)`
`            ``cout << str << endl;`
`    ``}`

`    ``// recurse for all children of root node`
`    ``for` `(``int` `i = 0; i < ALPHABET_SIZE; i++)`
`    ``{`
`        ``TrieNode* child = root->children[i];`
`        ``if` `(child)`
`            ``printAllWords(child);`
`    ``}`
`}`

`// search for pattern in Trie and print all words`
`// matching that pattern`
`bool` `search(TrieNode* root, string pattern)`
`{`
`    ``int` `index;`
`    ``TrieNode* pCrawl = root;`

`    ``for` `(``int` `level = 0; level < pattern.length(); level++)`
`    ``{`
`        ``index = ``int``(pattern[level]) - ``'A'``;`
`        ``// Invalid pattern`
`        ``if` `(!pCrawl->children[index])`
`            ``return` `false``;`

`        ``pCrawl = pCrawl->children[index];`
`    ``}`

`    ``// print all words matching that pattern`
`    ``printAllWords(pCrawl);`

`    ``return` `true``;`
`}`

`// Main function to print all words in the CamelCase`
`// dictionary that matches with a given pattern`
`void` `findAllWords(vector<string> dict, string pattern)`
`{`
`    ``// construct Trie root node`
`    ``TrieNode* root = getNewTrieNode();`

`    ``// Construct Trie from given dict`
`    ``for` `(string word : dict)`
`        ``insert(root, word);`

`    ``// search for pattern in Trie`
`    ``if` `(!search(root, pattern))`
`        ``cout << ``"No match found"``;`
`}`