Trie是一种有效的信息检索数据结构。使用Trie，可以使搜索复杂度达到最佳极限(密钥长度)。
任务是使用递归在Trie中搜索字符串。
例子 ：
root
/ \
t a
| |
h n
| | \
e s y
/ | |
i r w
| | |
r e e
|
r
Input : str = "anywhere"
Output : not found
Input : str = "answer"
Output : found方法 ：
搜索键类似于插入操作，但是，我们仅比较字符并向下移动。搜索可能由于字符串或Trie中缺少关键字而终止。在前一种情况下，如果最后一个节点的endOfWord字段为true，则该键存在于trie中。在第二种情况下，搜索将终止，而不检查键的所有字符，因为该键不在Trie中。
下面是上述方法的实现：
CPP
// 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 insert 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;
} Python3
# Python3 program to traverse in bottom up manner
CHILDREN = 26
MAX = 100
# Trie node
class trie:
def __init__(self):
self.child = [None for i in range(CHILDREN)]
# endOfWord is true if the node represents
# end of a word
self.endOfWord = False
# Function will return the new node(initialized to NULLs)
def createNode():
temp = trie()
return temp
# Function will insert the string in a trie recursively
def insertRecursively(itr, str, i):
if(i < len(str)):
index = ord(str[i]) - ord('a')
if(itr.child[index] == None ):
# Insert a new node
itr.child[index] = createNode();
# Recursive call for insertion of 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
def insert(itr, str):
# Function call with necessary arguments
insertRecursively(itr, str, 0);
# Function to search the string in a trie recursively
def searchRecursively(itr ,str, i, len):
# When a string or any character
# of a string is not found
if (itr == None):
return False
# Condition of finding string successfully
if (itr.endOfWord == True and i == len - 1):
# Return true when endOfWord
# of last node containes true
return True
index = ord(str[i]) - ord('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
def search(root, str):
arr = ['' for i in range(len(str) + 1)]
arr = str
# If string found
if (searchRecursively(root, arr, 0, len(str) + 1)):
print("found")
else:
print("not found")
# Driver code
if __name__=='__main__':
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")
# This code is contributed by rutvik_56输出：
not found
found