如何让 strcasecmp 比较字符串而不区分大小写

Question

我正在学习 C 语言的 cs50 在线课程，我有一个项目是编写一个函数，将字典（单词数据库）加载到内存中，有效地将其散列成散列 table 然后比较给定文本中的单词以检查拼写，必须比较不区分大小写。

完成此概述后，我遇到的主要问题是降低了大小写敏感性，因此我不确定下面的 strcasecmp 函数是怎么出错的。我知道内存泄漏，但稍后会解决它们。

下面是C:

中的代码

    
    //for the universal hash function
    #define BASE 256
    
    // Represents a node in a hash table
    typedef struct node
    {
        char word[LENGTH + 1];
        struct node *next;
    }
    node;
    
    // Number of buckets in hash table
    const unsigned int N = 676;
    
    // Hash table
    node *table[N];
    int word_count = 0;
    
    // Returns true if word is in dictionary else false
    //Require a search funtion
    bool check(const char *word)
    {
        int hashIndex = hash(word);
        for (node *tmp = table[hashIndex]; tmp != NULL; tmp = tmp->next)
        {
            
            if (strcasecmp(word, tmp->word) == 0)
            {
                return true;
            }
        }
        return false;
    }
    
    // Hashes word to a number
    // the dividing hash function is one I cited from the yale.edu page http://www.cs.yale.edu/homes/aspnes/pinewiki/C(2f)HashTables.html having worked with.
    unsigned int hash(const char *word)
    {
        unsigned long m = 11;
        unsigned long h;
        unsigned const char *us;
        //ensure element value is >= 0 
        us = (unsigned const char *) word;
      
        h = 0;
        while(*us != '[=10=]') 
        {
            h = (h * BASE + *us) % m;
            us++;
        } 
        return (h % N);
    }

当使用 CS50 提供的 check50 函数进行检查时，我得到：

> :( spell-checking is case-insensitive expected "MISSPELLED WOR...",
> not "MISSPELLED WOR..." Log running ./speller case/dict case/text...
> checking for output "MISSPELLED WORDS\n\n\nWORDS MISSPELLED: 0\nWORDS
> IN DICTIONARY: 1\nWORDS IN TEXT: 8\n"...
> 
> Expected Output: MISSPELLED WORDS
> 
> 
> WORDS MISSPELLED:     0 WORDS IN DICTIONARY:  1 WORDS IN TEXT:       
> 8 Actual Output: MISSPELLED WORDS
> 
> foO fOo Foo fOO FoO FOo FOO
> 
> WORDS MISSPELLED:     7 WORDS IN DICTIONARY:  1 WORDS IN TEXT:       
> 8
> 
> :( handles most basic words properly expected "MISSPELLED WOR...", not
> "MISSPELLED WOR..." Log running ./speller basic/dict basic/text...
> checking for output "MISSPELLED WORDS\n\n\nWORDS MISSPELLED: 0\nWORDS
> IN DICTIONARY: 8\nWORDS IN TEXT: 9\n"...
> 
> Expected Output: MISSPELLED WORDS
> 
> 
> WORDS MISSPELLED:     0 WORDS IN DICTIONARY:  8 WORDS IN TEXT:       
> 9 Actual Output: MISSPELLED WORDS
> 
> The
> 
> WORDS MISSPELLED:     1 WORDS IN DICTIONARY:  8 WORDS IN TEXT:       
> 9

主要问题是：如何在不区分大小写的情况下比较两个字符串？

Answer 1

if (strcasecmp(word, tmp->word) == 0) 并不是单词大小写重要的唯一地方。 hash 呢？它还需要考虑字母大小写，例如 'A' 和 'a' 将散列为不同的值。

如何让 strcasecmp 比较字符串而不区分大小写

How can I get strcasecmp to compare strings without being case sensitive

c

cs50