特里(显示内容)

Trie是一种有效的信息检索数据结构。在上一篇有关trie的文章中，我们讨论了trie的基础知识以及如何在trie中插入和搜索键。在这篇文章中，我们将讨论有关显示Trie的所有内容的信息。也就是说，显示Trie中存在的所有键。

例子：

Input: If Trie is      root
                    /   \    \
                    t   a     b
                    |   |     |
                    h   n     y
                    |   |  \  |
                    e   s  y  e
                 /  |   |
                 i  r   w
                 |  |   |
                 r  e   e
                        |
                        r
Output: Contents of Trie:
        answer
        any
        bye
        their
        there

这样做的想法是从trie的根节点开始遍历，每当我们找到NON-NULL子节点时，就在当前索引(级别)的“字符串 str”中添加子节点的父键，然后递归调用对子节点进行相同的处理，然后进行相同的处理，直到找到该节点(即叶节点)为止，该节点实际上标记了字符串。
以下是上述想法的C++实现：

// CPP program to display content of Trie
#include 
#include 
#define alpha_size 26
#define ARRAY_SIZE(a) sizeof(a) / sizeof(a[0])
  
using namespace std;
  
// Trie node
struct TrieNode 
{
    struct TrieNode* children[alpha_size];
  
    bool isLeaf;
};
  
// Returns new trie node (initialized to NULLs)
struct TrieNode* createNode()
{
    struct TrieNode* pNode = new TrieNode;
  
    for (int i = 0; i < alpha_size; i++)
        pNode->children[i] = NULL;
  
    pNode->isLeaf = false;
  
    return pNode;
};
  
// function to insert a node in Trie
void insert_node(struct TrieNode* root, char* key)
{
    int level;
    int length = strlen(key);
    struct TrieNode* pCrawl = root;
  
    for (level = 0; level < length; level++) 
    {
        int index = key[level] - 'a';
  
        if (pCrawl->children[index] == NULL)
            pCrawl->children[index] = createNode();
  
        pCrawl = pCrawl->children[index];
    }
  
    pCrawl->isLeaf = true;
}
  
// function to check if current node is leaf node or not
bool isLeafNode(struct TrieNode* root)
{
    return root->isLeaf != false;
}
  
// function to display the content of Trie
void display(struct TrieNode* root, char str[], int level)
{
    // If node is leaf node, it indicates end
    // of string, so a null character is added
    // and string is displayed
    if (isLeafNode(root)) 
    {
        str[level] = '\0';
        cout << str << endl;
    }
  
    int i;
    for (i = 0; i < alpha_size; i++) 
    {
        // if NON NULL child is found
        // add parent key to str and
        // call the display function recursively
        // for child node
        if (root->children[i]) 
        {
            str[level] = i + 'a';
            display(root->children[i], str, level + 1);
        }
    }
}
  
// Driver program to test above functions
int main()
{
    // Keys to be inserted in Trie
    char keys[][8] = { "the", "a", "there", "answer",
                       "any", "by", "bye", "their" };
  
    struct TrieNode* root = createNode();
  
    // Inserting keys in Trie
    for (int j = 0; j < ARRAY_SIZE(keys); j++)
        insert_node(root, keys[j]);
  
    int level = 0;
    char str[20];
  
    // Displaying content of Trie
    cout << "Content of Trie: " << endl;
    display(root, str, level);
}

输出：

Content of Trie:
a
answer
any
by
bye
the
their
there

注意：上面的算法按Lexographically Sorted顺序显示Trie的内容。

Trie的一些有用的应用程序是：

• 实现自动更正和自动完成功能
• 实施字典