Trie 字典树 删除操作

字典树的删除操作：

1 没找到直接返回

2 找到叶子节点的时候，叶子节点的count标志清零，代表不是叶子节点了

3 如果当前节点没有其他孩子节点的时候，可以删除这个节点

判断是否需是叶子节点，就检查叶子节点的count标志就可以了。

判断是否有其他孩子节点就需要循环26个节点了，如果都为空，那么就没有其他孩子节点了。

#include 
#include 
#include 
#include 
#include 

class TrieDelete_2
{
	static const int ARRAY_SIZE = 26;
	struct Node
	{
		int val;
		Node *children[ARRAY_SIZE];
		explicit Node(int k = 0) : val(k)
		{
			for (int i = 0; i < ARRAY_SIZE; i++)
			{
				children[i] = NULL;
			}
		}
		~Node()
		{
			for (int i = 0; i < ARRAY_SIZE; i++)
			{
				if (children[i]) delete children[i];
				children[i] = NULL;
			}
		}
	};

	struct Trie
	{
		Node *emRoot;
		int count;
		explicit Trie(int c = 0) : count(c)
		{
			emRoot = new Node;//emRoot(NULL) {},应该分配emRot空间比较合理
		}
		~Trie()
		{
			if (emRoot) delete emRoot;
			emRoot = NULL;
		}
	};

	void insert(Trie *trie, char keys[])
	{
		int len = strlen(keys);

		Node *pCrawl = trie->emRoot;
		trie->count++;

		for (int i = 0; i < len; i++)
		{
			int k = keys[i] - 'a';
			if (!pCrawl->children[k])
			{
				pCrawl->children[k] = new Node;
			}
			pCrawl = pCrawl->children[k];
		}
		pCrawl->val = trie->count;
	}

	bool search(Trie *trie, char key[])
	{
		int len = strlen(key);
		Node *pCrawl = trie->emRoot;
		for (int i = 0; i < len; i++)
		{
			int k = key[i] - 'a';
			if (!pCrawl->children[k])
			{
				return false;
			}
			pCrawl = pCrawl->children[k];
		}
		return pCrawl->val != 0;
	}

	bool isFreeNode(Node *n)
	{
		for (int i = 0; i < ARRAY_SIZE; i++)
		{
			if (n->children[i]) return false;
		}
		return true;
	}

	bool isLeaf(Node *n)
	{
		return n->val != 0;
	}

	bool deleteHelp(Node *n, char key[], int lv, int len)
	{
		if (n)
		{
			if (lv == len)
			{
				if (isLeaf(n))
				{
					n->val = 0;
					if (isFreeNode(n))
					{
						delete n, n = NULL;
						return true;
					}
					return false;
				}
			}
			else
			{
				int k = key[lv] - 'a';
				if(deleteHelp(n->children[k], key, lv+1, len))
				{
					if (!isLeaf(n) && isFreeNode(n))
					{
						delete n, n = NULL;
						return true;
					}
					return false;
				}
			}
		}
		return false;
	}

	void deleteKey(Trie *trie, char key[])
	{
		int len = strlen(key);
		if (len > 0)
		{
			deleteHelp(trie->emRoot, key, 0, len);
		}
	}

public:
	TrieDelete_2()
	{
		char keys[][8] = {"she", "sells", "sea", "shore", "the", "by", "sheer"};
		Trie *trie = new Trie; 

		for(int i = 0; i < ARRAY_SIZE(keys); i++)
		{
			insert(trie, keys[i]);
		}

		deleteKey(trie, keys[0]);

		printf("%s %s\n", "she", search(trie, "she") ? "Present in trie" : "Not present in trie");

		delete trie;
	}
};