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原题题目

代码实现（首刷绝大部分自解）

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     struct TreeNode *left; *     struct TreeNode *right; * }; *//** Encodes a tree to a single string. */char* serialize(struct TreeNode* root){
   //基本思路 层序遍历if(!root)        return NULL;    char* tree = (char*)malloc(sizeof(char) * 100000);        //这里的charpos是记录字符串当前到什么位置了    int size = 0,rear = -1,top = -1,charpos = 0;    struct TreeNode* queue[50000],*pos = root;    queue[++rear] = pos;    while(rear != top)    {
           size = rear - top;         while(size--)        {
               pos = queue[++top];            if(!pos)                charpos += sprintf(tree+charpos,",%s","null");            else            {
                   if(!top)                    charpos += sprintf(tree+charpos,"%d",pos->val);                else                    charpos += sprintf(tree+charpos,",%d",pos->val);                    				//当存在时 则导入其节点 不存在时 则放入NULL 方便检测                if(pos->left) queue[++rear] = pos->left;                else queue[++rear] = NULL;                if(pos->right) queue[++rear] = pos->right;                else queue[++rear] = NULL;            }        }        //当只存在空结点时 则退出循坏        if(rear - top == nullnumbers)            break;    }    return tree;}/** Decodes your encoded data to tree. */struct TreeNode* deserialize(char* data) {
   if(!data)        return NULL;            //这里是设定最小值    const int MIN = -99999;    int numpos = 0,charpos = 0,num[50000],number,tempnumpos = 0,nextlevel;    struct TreeNode* stack[50000],*realroot,*root;    bool flag;//flag的作用是检测是否为负数 因为负数占两个格子	//下面的while主要将有效数字提取出来 变成数组    while(charpos < strlen(data))    {
           flag = false;        if(data[charpos] == ',')            charpos++;        number = 0;                //当出现负数时        if(data[charpos] == '-')        {
               flag = true;            charpos++;        }        if(data[charpos] >= '0' && data[charpos] <= '9')        {
               while(data[charpos] >= '0' && data[charpos] <='9')                number = number*10 + data[charpos++] - '0';            if(!flag)                num[numpos++] = number;            else                num[numpos++] = -number;        }        else        {
               num[numpos++] = MIN;            charpos += 4;        }    }	//创建根节点    realroot = (struct TreeNode*)malloc(sizeof(struct TreeNode));    realroot->val = num[tempnumpos];    realroot->left = realroot->right = NULL;    stack[tempnumpos] = realroot;	//nextlevel的作用是 确定左右节点的在数组中的位置    nextlevel = tempnumpos+1;    while(tempnumpos < numpos)    {
           if(num[tempnumpos] != MIN)        {
               if(nextlevel < numpos && num[nextlevel] != MIN)            {
                   root = (struct TreeNode*)malloc(sizeof(struct TreeNode));                root->val = num[nextlevel];                root->right = root->left = NULL;                stack[tempnumpos]->left = root;                stack[nextlevel] = root;            }            else                stack[tempnumpos]->left = NULL;            //向下移动位置            nextlevel++;            if(nextlevel < numpos && num[nextlevel] != MIN)            {
                   root = (struct TreeNode*)malloc(sizeof(struct TreeNode));                root->val = num[nextlevel];                root->left = root->right = NULL;                stack[tempnumpos]->right = root;                stack[nextlevel] = root;            }            else                stack[tempnumpos]->right = NULL;            //向下移动位置            nextlevel++;        }        tempnumpos++;    } while(tempnumpos < numpos);    return realroot;}// Your functions will be called as such:// char* data = serialize(root);// deserialize(data);

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