449. 序列化和反序列化二叉搜索树

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/**
 * 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 single string.
    string serialize(TreeNode* root) {
        vector<int>v;
        postorder(root,v);
        string s;
        if(v.size()==0)return s;
        for(int i=0;i<v.size()-1;i++)
            s.append(to_string(v[i])+",");
        s.append(to_string(v.back()));
        return s;
    }
    void postorder(TreeNode *T,vector<int>&v)
    {
        if(!T)return;
        if(T->left)postorder(T->left,v);
        if(T->right)postorder(T->right,v);
        v.push_back(T->val);
    }
    vector<string>split(string s,char c)
    {
        vector<string>v;
        int t=0;
        int start=0;
        while(t<s.size())
        {
            while(t<s.size()&&s[t]==c)t++;
            start=t;
            while(t<s.size()&&s[t]!=c)t++;
            if(start<s.size())v.push_back(s.substr(start,t-start));
        }
        return v;
    }
    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        if(data.size()==0)return nullptr;
        vector<string>v=split(data,',');
        int in[10010],pos[10010];
        int cnt=0;
        for(auto x:v)
        {
            in[cnt]=stoi(x);
            pos[cnt]=stoi(x);
            cnt++;
        }
        sort(in,in+cnt);
        return create(cnt,in,pos);
    }
    TreeNode* create(int len,int *in,int *pos)
    {
        if(len<=0)return nullptr;
        TreeNode *T=new TreeNode(pos[len-1]);
        T->left=T->right=nullptr;
        int i=0;
        for(i=0;i<len;i++)
            if(T->val==in[i])
                break;
        T->left=create(i,in,pos);
        T->right=create(len-i-1,in+i+1,pos+i);
        return T;
    }
};

// Your Codec object will be instantiated and called as such:
// Codec* ser = new Codec();
// Codec* deser = new Codec();
// string tree = ser->serialize(root);
// TreeNode* ans = deser->deserialize(tree);
// return ans;