c - 在C中的双链表中添加 child

Question

我有一个结构定义为:

struct ac {
    int value;
    char character; 
    char * word;
    struct ac *next;
    struct ac *previous;
    struct ac *child;
    struct ac *parent;
};

当一个单词的末尾包含相同字符两次或更多次时，我特别有问题。

// 'w' is the word input
int depth = 0;
ac *a; // is struct that is size of ac and contains all of the struct values set either to NULL or 0.
while(w[depth] != '\0'){
    if (a -> character == w[depth]) {
        if ((a -> value == 0) && (w[depth +1] == '\0')) {
            a -> value = 1;
            a -> word = malloc(strlen(w)+1);
            strcpy(a -> word, w);
        }
        printf("follow existing path %c\n", w[depth]);
        a = a -> child;
        depth ++;
    }
// word() is a function that reserves memory for the new word and initializes new_word problaply not relevent for this question.
    else if (a -> child == NULL) {
        new_word = word(w,depth);
        new_word -> parent = a;
        printf("create child %c\n", w[depth]);
        a -> child = new_word;
        a = new_word;
        depth ++;
    }
}

例如，当输入单词“well”时，将打印以下输出:

• 创建 child w
• 创建子e
• 创建子l
• 遵循现有路径 l

但是这最后一个'follow existing path l'应该是'create child l'

而且我似乎想不出会歧视最后一个“l”的条件。有人可以帮我解决这个问题吗？将不胜感激。

Answer 1

问题是你没有正确地向前看。您应该检查 a->child 是否为 NULL 首先，如果是，则添加一个新节点，然后移动到该子节点。

如果 a->child 不是 NULL，那么你应该将 a->child->character 与当前字符进行比较，并且如果匹配，则移动到 a->child。

我认为它应该是这样的:

int depth = 0;
ac *a;
while (w[depth] != '\0') {
    if (a->child == NULL) {
        new_word = word(w,depth);
        new_word->parent = a;
        printf("create child %c\n", w[depth]);
        a->child = new_word;
        a = new_word;
        depth ++;
    }
    else if (a->child->character == w[depth]) {
        if ((a->child->value == 0) && (w[depth +1] == '\0')) {
            a->child->value = 1;
            a->child->word = malloc(strlen(w)+1);
            strcpy(a->child->word, w);
        }
        printf("follow existing path %c\n", w[depth]);
        a = a->child;
        depth ++;
    }
}