トライ木を解放する

Question

私はトライ木の例をいくつか見つけ出し、辞書にあるすべての単語のトライ木を含むゲームを手伝うためにそれらを試してみました。私の例では、メモリリークを避けるためにfreeTreeを実装していないので、私は自分自身で作成しようとしています。しかし、私はしばらくのうちにcで働いておらず、問題にぶつかっています。

char keys[][8] = {"the", "a", "there", "answer", "any", 
       "by", "bye", "their"}; 
char output[][32] = {"Not present in trie", "Present in trie"}; 
struct TrieNode *root = getNode(); 

// Construct trie 
int i; 
for (i = 0; i < ARRAY_SIZE(keys); i++){ 
    insert(root, keys[i]); 
} 

// Search for different keys 
printf("%s --- %s\n", "the", output[search(root, "the")]); 
printf("%s --- %s\n", "these", output[search(root, "these")]); 
printf("%s --- %s\n", "their", output[search(root, "their")]); 
printf("%s --- %s\n", "thaw", output[search(root, "thaw")]); 

freeTree(root); 

printf("test after free\n"); 
printf("%s --- %s\n", "the", output[search(root, "the")]); 
printf("%s --- %s\n", "these", output[search(root, "these")]); 
printf("%s --- %s\n", "their", output[search(root, "their")]); 
printf("%s --- %s\n", "thaw", output[search(root, "thaw")]); 

これは簡単なテストイム実行されていて、自由な後の結果がここに

the --- Present in trie 
these --- Not present in trie 
their --- Present in trie 
thaw --- Not present in trie 
test after free 
the --- Present in trie 
these --- Not present in trie 
their --- Present in trie 
thaw --- Not present in trie 

前と同じですが

struct TrieNode 
{ 
    struct TrieNode *children[ALPHABET_SIZE]; 
    bool isLeaf; 
}; 

を用いた構造イムとフリーな実装である

void freeChildren(struct TrieNode *node){ 
    int i; 
    if (node->isLeaf == false){ 
     for (i=0;i<ALPHABET_SIZE;i++){ 
     if (node->children[i] != NULL){ 
      freeChildren(node->children[i]); 
     } 
     } 
    } 

    if (node != NULL){ 
     node = NULL; 
     free(node); 
    } 
} 

void freeTree(struct TrieNode *root){ 
    freeChildren(root); 
    free(root); 
} 

Wh私は新しいツリーノードを作成します。私はそのためにメモリをmallocします。私は自由にする必要があることを知っています。

Answer 1

void freeChildren(struct TrieNode *node){ 
    int i; 
    if (node != NULL && node->isLeaf == false){//NULL check important only for the root 
     for (i=0;i<ALPHABET_SIZE;i++){ 
     if (node->children[i] != NULL){ 
      freeChildren(node->children[i]); 
      node->children[i] = NULL]; //you have to remove the address, otherwise it stays, just is no longer allocated (but it is still possible to access it, though it might crash or do whatever else) 
     } 
     } 
    } 

    if (node != NULL){ //again only root could be NULL 
     free(node);//this has to go first 
     //node = NULL; this has no meaning, as this is the local variable, not the place you passed it to 
    } 
} 

void freeTree(struct TrieNode *root){ 
    freeChildren(root); 
    // free(root); this is already done in the freeChildren 
    // you might want to realloc the root there though, as otherwise you don't have anything allocated to root 
    root = NULL; 
} 

Answer 2

私はあなたの問題はこの部分だと思う：

if (node != NULL){ 
    node = NULL; 
    free(node); 
} 

さて、あなたはNULLに設定し、それを解放する必要があります。それ以外の場合は、すでにアドレスを失ってしまいます。