37：序列化二叉树

前序遍历序列化和反序列化

class Solution {
public:
    char* Serialize(TreeNode *root) {    
        if(!root)return "#";
        string s=to_string(root->val);
        s.push_back(',');
        char *left=Serialize(root->left);
        char *right=Serialize(root->right);
        char *ret=new char[s.size()+strlen(left)+strlen(right)];
        strcpy(ret,s.c_str());
        strcat(ret,left);
        strcat(ret,right);
        return ret;
    }
    TreeNode* Deserialize(char *str) {
        return decode(str);
    }
    TreeNode* decode(char* &str)
    {
        if(*str=='#')
        {
            str++;
            return NULL;
        }
        int num=0;
        while(*str!=',')num=num*10+*str-'0',str++;
        str++;
        TreeNode* root=new TreeNode(num);
        root->left=decode(str);
        root->right=decode(str);
        return root;
    }
};