# Search in a trie Recursively

Trie is an efficient information retrieval data structure. Using Trie, search complexities can be brought to an optimal limit (key length).

The task is to search a string in a Trie using recursion.

Examples :

```                                          root
/  \
t   a
|   |
h   n
|   |  \
e   s   y
/  |   |
i   r   w
|   |   |
r  e   e
|
r

Input : str = "anywhere"

Output : found
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach :
Searching a key is similar to insertion operation, however, we only compare the characters and move down. The search can terminate due to the end of a string or lack of key in the trie. In the former case, if the endOfWord field of the last node is true, then the key exists in the trie. In the second case, the search terminates without examining all the characters of the key, since the key is not present in the trie.

Below is the implementation of the above approach :

 `// CPP program to search in a trie ` `#include ` `using` `namespace` `std; ` `#define CHILDREN 26 ` `#define MAX 100 ` ` `  `// Trie node ` `struct` `trie { ` `    ``trie* child[CHILDREN]; ` `    ``// endOfWord is true if the node represents ` `    ``// end of a word ` `    ``bool` `endOfWord; ` `}; ` ` `  `// Function will return the new node(initialized to NULLs) ` `trie* createNode() ` `{ ` `    ``trie* temp = ``new` `trie(); ` `    ``temp->endOfWord = ``false``; ` `    ``for` `(``int` `i = 0; i < CHILDREN; i++) { ` `        ``// initially assign null to the all child ` `        ``temp->child[i] = NULL; ` `    ``} ` `    ``return` `temp; ` `} ` `/*function will inert the string in a trie recursively*/` `void` `insertRecursively(trie* itr, string str, ``int` `i) ` `{ ` `    ``if` `(i < str.length()) { ` `        ``int` `index = str[i] - ``'a'``; ` `        ``if` `(itr->child[index] == NULL) { ` ` `  `            ``// Insert a new node ` `            ``itr->child[index] = createNode(); ` `        ``} ` `        ``// Recursive call for insertion of a string ` `        ``insertRecursively(itr->child[index], str, i + 1); ` `    ``} ` `    ``else` `{ ` `        ``// Make the endOfWord true which represents ` `        ``// the end of string ` `        ``itr->endOfWord = ``true``; ` `    ``} ` `} ` `// Function call to insert a string ` `void` `insert(trie* itr, string str) ` `{ ` `    ``// Function call with necessary arguments ` `    ``insertRecursively(itr, str, 0); ` `} ` ` `  `// Function to search the string in a trie recursively ` `bool` `searchRecursively(trie* itr, ``char` `str[], ``int` `i, ` `                                               ``int` `len) ` `{ ` `    ``// When a string or any character  ` `    ``// of a string is not found ` `    ``if` `(itr == NULL) ` `        ``return` `false``; ` ` `  `    ``// Condition of finding string successfully ` `    ``if` `(itr->endOfWord == ``true` `&& i == len - 1) { ` `        ``// Return true when endOfWord  ` `        ``// of last node containes true ` `        ``return` `true``; ` `    ``} ` ` `  `    ``int` `index = str[i] - ``'a'``; ` `    ``// Recursive call and return  ` `    ``// value of function call stack ` `    ``return` `searchRecursively(itr->child[index],  ` `                                   ``str, i + 1, len); ` `} ` ` `  `// Function call to search the string ` `void` `search(trie* root, string str) ` `{ ` `    ``char` `arr[str.length() + 1]; ` `    ``strcpy``(arr, str.c_str()); ` `    ``// If string found ` `    ``if` `(searchRecursively(root, arr, 0, str.length() + 1)) ` `        ``cout << ``"found"` `<< endl; ` ` `  `    ``else` `{ ` `        ``cout << ``"not found"` `<< endl; ` `    ``} ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``trie* root = createNode(); ` ` `  `    ``// Function call to insert the string ` `    ``insert(root, ``"thier"``); ` `    ``insert(root, ``"there"``); ` `    ``insert(root, ``"answer"``); ` `    ``insert(root, ``"any"``); ` ` `  `    ``// Function call to search the string ` `    ``search(root, ``"anywhere"``); ` `    ``search(root, ``"answer"``); ` ` `  `    ``return` `0; ` `} `

Output:

```not found
found
```

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