关于uthash的问题，小白求教!

w4846383 2022-10-02 11:43:26

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "D:\uthash库\uthash.h"
#include "xuliehua.h"


/*
struct TreeNode {
	int val;
	struct TreeNode* left;
	struct TreeNode* right;
};
*/



 /**
  * Note: The returned array must be malloced, assume caller calls free().
  */
typedef struct hashnode {
    char key[20000];
    struct TreeNode* node;
    int cnt;
    UT_hash_handle hh;
}Hashnode;

char * mydfs(struct TreeNode* root, Hashnode* USER)
{
    if (root == NULL)    //到达叶子节点后面的空节点
        return "#";

    char* string = (char*)calloc(20000, sizeof(char));
    sprintf(string, "%d", root->val);                     //将当前节点val存入字符串
    strcat(string, mydfs(root->left, USER));              //该字符串衔接左节点形成的字符串
    strcat(string, mydfs(root->right, USER));             //该字符串衔接右节点形成的字符串

    Hashnode* tm = NULL;
    HASH_FIND_STR(USER, string, tm);                      //以该字符串为key，查找hashmap
    if (tm == NULL)
    {
        tm = (Hashnode*)calloc(1, sizeof(Hashnode));
        strcpy(tm->key, string);
        tm->node = root;
        tm->cnt = 1;
        HASH_ADD_STR(USER, key, tm);
    }
    else
        tm->cnt++;

    return string;
}

struct TreeNode** findDuplicateSubtrees(struct TreeNode* root, int* returnSize) {
    if (root == NULL)
    {
        *returnSize = 0;
        return NULL;
    }

    Hashnode* USER = NULL;
    mydfs(root, USER);
    int len = HASH_COUNT(USER);
    struct TreeNode** res = (struct TreeNode**)calloc(len, sizeof(struct TreeNode));
    Hashnode* cur, * tm;
    HASH_ITER(hh, USER, cur, tm)
    {
        if (cur->cnt > 1)
        {
            res[(*returnSize)++] = cur->node;
        }
        free(cur);
    }
    free(USER);

    return res;

}

如上代码是力扣中的题目：寻找重复的子树。

现在的问题是，程序执行完之后USER是空的，调试了也发现每次递归之后USER就成NULL了，请问这是什么原因造成的呢？

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