Trie用于存储字典单词，以便可以有效地搜索它们并可以进行前缀搜索。任务是编写一个函数来计算单词数。
例子 ：
Input : root
/ \ \
t a b
| | |
h n y
| | \ |
e s y e
/ | |
i r w
| | |
r e e
|
r
Output : 8
Explanation : Words formed in the Trie :
"the", "a", "there", "answer", "any", "by",
"bye", "their".
在Trie结构中，我们有一个字段来存储单词标记的末尾，在下面的实现中我们将其称为isLeaf。要计算单词数，我们只需要遍历Trie并计算设置了isLeaf的所有节点。
C++
// C++ implementation to count words in a trie
#include
using namespace std;
#define ARRAY_SIZE(a) sizeof(a)/sizeof(a[0])
// Alphabet size (# of symbols)
#define ALPHABET_SIZE (26)
// Converts key current character into index
// use only 'a' through 'z' and lower case
#define CHAR_TO_INDEX(c) ((int)c - (int)'a')
// Trie node
struct TrieNode
{
struct TrieNode *children[ALPHABET_SIZE];
// isLeaf is true if the node represents
// end of a word
bool isLeaf;
};
// Returns new trie node (initialized to NULLs)
struct TrieNode *getNode(void)
{
struct TrieNode *pNode = new TrieNode;
pNode->isLeaf = false;
for (int i = 0; i < ALPHABET_SIZE; i++)
pNode->children[i] = NULL;
return pNode;
}
// If not present, inserts key into trie
// If the key is prefix of trie node, just
// marks leaf node
void insert(struct TrieNode *root, const char *key)
{
int length = strlen(key);
struct TrieNode *pCrawl = root;
for (int level = 0; level < length; level++)
{
int index = CHAR_TO_INDEX(key[level]);
if (!pCrawl->children[index])
pCrawl->children[index] = getNode();
pCrawl = pCrawl->children[index];
}
// mark last node as leaf
pCrawl->isLeaf = true;
}
// Function to count number of words
int wordCount(struct TrieNode *root)
{
int result = 0;
// Leaf denotes end of a word
if (root -> isLeaf)
result++;
for (int i = 0; i < ALPHABET_SIZE; i++)
if (root -> children[i])
result += wordCount(root -> children[i]);
return result;
}
// Driver
int main()
{
// Input keys (use only 'a' through 'z'
// and lower case)
char keys[][8] = {"the", "a", "there", "answer",
"any", "by", "bye", "their"};
struct TrieNode *root = getNode();
// Construct Trie
for (int i = 0; i < ARRAY_SIZE(keys); i++)
insert(root, keys[i]);
cout << wordCount(root);
return 0;
} Java
// Java implementation to count words in a trie
public class Words_in_trie {
// Alphabet size (# of symbols)
static final int ALPHABET_SIZE = 26;
// Trie node
static class TrieNode
{
TrieNode[] children = new TrieNode[ALPHABET_SIZE];
// isLeaf is true if the node represents
// end of a word
boolean isLeaf;
TrieNode(){
isLeaf = false;
for (int i = 0; i < ALPHABET_SIZE; i++)
children[i] = null;
}
};
static TrieNode root;
// If not present, inserts key into trie
// If the key is prefix of trie node, just
// marks leaf node
static void insert(String key)
{
int length = key.length();
TrieNode pCrawl = root;
for (int level = 0; level < length; level++)
{
int index = key.charAt(level) - 'a';
if (pCrawl.children[index] == null)
pCrawl.children[index] = new TrieNode();
pCrawl = pCrawl.children[index];
}
// mark last node as leaf
pCrawl.isLeaf = true;
}
// Function to count number of words
static int wordCount(TrieNode root)
{
int result = 0;
// Leaf denotes end of a word
if (root.isLeaf)
result++;
for (int i = 0; i < ALPHABET_SIZE; i++)
if (root.children[i] != null )
result += wordCount(root.children[i]);
return result;
}
// Driver Program
public static void main(String args[])
{
// Input keys (use only 'a' through 'z'
// and lower case)
String keys[] = {"the", "a", "there", "answer",
"any", "by", "bye", "their"};
root = new TrieNode();
// Construct Trie
for (int i = 0; i < keys.length; i++)
insert(keys[i]);
System.out.println(wordCount(root));
}
}
// This code is contributed by Sumit GhoshC#
// C# implementation to count words in a trie
using System;
public class Words_in_trie
{
// Alphabet size (# of symbols)
static readonly int ALPHABET_SIZE = 26;
// Trie node
public class TrieNode
{
public TrieNode[] children = new TrieNode[ALPHABET_SIZE];
// isLeaf is true if the node represents
// end of a word
public bool isLeaf;
public TrieNode()
{
isLeaf = false;
for (int i = 0; i < ALPHABET_SIZE; i++)
children[i] = null;
}
};
static TrieNode root;
// If not present, inserts key into trie
// If the key is prefix of trie node, just
// marks leaf node
static void insert(String key)
{
int length = key.Length;
TrieNode pCrawl = root;
for (int level = 0; level < length; level++)
{
int index = key[level] - 'a';
if (pCrawl.children[index] == null)
pCrawl.children[index] = new TrieNode();
pCrawl = pCrawl.children[index];
}
// mark last node as leaf
pCrawl.isLeaf = true;
}
// Function to count number of words
static int wordCount(TrieNode root)
{
int result = 0;
// Leaf denotes end of a word
if (root.isLeaf)
result++;
for (int i = 0; i < ALPHABET_SIZE; i++)
if (root.children[i] != null )
result += wordCount(root.children[i]);
return result;
}
// Driver code
public static void Main()
{
// Input keys (use only 'a' through 'z'
// and lower case)
String []keys = {"the", "a", "there", "answer",
"any", "by", "bye", "their"};
root = new TrieNode();
// Construct Trie
for (int i = 0; i < keys.Length; i++)
insert(keys[i]);
Console.WriteLine(wordCount(root));
}
}
/* This code contributed by PrinciRaj1992 */输出：
8