leetcode 297. Serialize and Deserialize Binary Tree

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

For example, you may serialize the following tree

    1
   / \
  2   3
     / \
    4   5
as  "[1,2,3,null,null,4,5]" , just the same as  how LeetCode OJ serializes a binary tree . You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.




class Codec {
	string my_itoa(int n)
	{
		if (n == 0)
			return "0";
		bool positive = n < 0 ? false : true;
		n = abs(n);
		string re;
		while (n != 0)
		{
			re.insert(re.begin(), n % 10 + '0');
			n /= 10;
		}
		if (!positive)
			re.insert(re.begin(), '-');
		return re;
	}
	int my_atoi(string s)
	{
		bool posivtive = s.front() != '-';
		if (s.front() == '-')
			s.erase(0, 1);
		int re = 0;
		while (!s.empty())
		{
			re = 10 * re + s[0] - '0';
			s.erase(0, 1);
		}
		if (!posivtive)
			re = -re;
		return re;
	}
public:
	// Encodes a tree to a single string.
	string serialize(TreeNode* root) {
		if (root == NULL)
			return "#";
		string s;
		vector<TreeNode*>que;
		que.push_back(root);
		while (!que.empty())
		{
			TreeNode*n = que.back();
			que.pop_back();
			if (n == NULL)
				s += "#,";
			else
			{
				s += my_itoa(n->val)+',';
				que.push_back(n->right);
				que.push_back(n->left);
			}
		}
		if (s.back() == ',')
			s.pop_back();
		return s;
	}

	// Decodes your encoded data to tree.
	TreeNode* deserialize(string data) {
		if (data == "#")
			return NULL;
		TreeNode*root = NULL;
		int pos = data.find(',');
		vector<TreeNode*>que;
		while (!data.empty())
		{
			string s;
			if (pos != string::npos)
			{
				s = string(data.begin(), data.begin() + pos);
				data.erase(0, pos + 1);
			}
			else
			{
				s = data;
				data.clear();
			}
			if (s == "#")
			{
				if (que.back()->left != NULL)
				{
					que.pop_back();
					pos = data.find(',');
					continue;
				}
				pos = data.find(',');
				if (pos != string::npos)
				{
					s = string(data.begin(), data.begin() + pos);
					data.erase(0, pos + 1);
				}
				else
				{
					s = data;
					data.clear();
				}
				
				if (s == "#")
					que.pop_back();
				else
				{
					int val = my_atoi(s);
					TreeNode*n = new TreeNode(val);
					que.back()->right = n;
					que.pop_back();
					que.push_back(n);
				}
			}
			else
			{
				int val = my_atoi(s);
				if (root == NULL)
				{
					root = new TreeNode(val);
					que.push_back(root);
				}
				else
				{
					TreeNode*n = new TreeNode(val);
					if (que.back()->left == NULL)
					{
						que.back()->left = n;
						que.push_back(n);
					}
					else
					{
						que.back()->right = n;
						que.pop_back();
						que.push_back(n);
					}
				}
			}
			pos = data.find(',');
		}
		return root;
	}
};

accept



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