2020-5 leetcode 297. 二叉树的序列化与反序列化

1.关键就是序列的格式：因为是返回字符串，那么怎么保证1.节点的值可以很方便的找到。2.节点的左右孩子可以很方便的找到

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Codec {
public:

    // Encodes a tree to a singlestring.
    string serialize(TreeNode* root) {
        if(root==NULL) return "";
        return to_string(root->val) +"["+serialize(root->left)+ "," + serialize(root->right)+"]";
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        stack<TreeNode*> s;
        TreeNode* root=NULL;
        string val;

        for(int i=0;i<data.size();i++){
            char t=data[i];
            if(t>='0'&&t<='9'||t=='-'){
                val+=t;
            }
            if(t=='['||(t==','&&data[i-1]=='[')||(t==']'&&data[i-1]==',')){
                TreeNode* node=NULL;
                if(!val.empty()) node=new TreeNode(stoi(val));
                if(root==NULL) root=node;
                val.clear();
                s.push(node);
            }
            if(t==','||t==']'){
                TreeNode* tp=s.top();
                s.pop();
                TreeNode* tmp=s.top();
                if(t==',') tmp->left=tp;
                else tmp->right=tp;
            }
        }
        return root;
    }
};

// Your Codec object will be instantiated and called as such:
// Codec codec;
// codec.deserialize(codec.serialize(root));