试图制作一个打印首字母缩略词的程序

人们已经在评论中解决了您的基本问题。如果您仍然遇到问题，这里有一个可以帮助您解决问题的有效程序。我做了两个根本性的改变。首先，正如其他人所讨论的，您不能返回一个局部变量数组。所以，我在 main 中声明了它并将它作为参数传递。其次，检查前一个字符是否不是字母有一个边缘情况，即您在第一个字符（即索引 0）上。在这种情况下，您无法检查一个字符，因为这会将您带到不存在的索引-1。所以，我首先有一个特殊的while循环来处理首字母缩略词的第一个字母。

在第一个字母之后，类似的东西就可以正常工作了。

我并不是说我的函数是最好的方法或唯一的方法，某些事情我没有解决。例如，我不检查结果数组是否会溢出。但是，为了您的目的，我只是在 main 中使 result 足够大，以便您提供的示例短语不会发生这种情况。但是，根据您提供的内容，它有效，我希望它有助于解决问题。

#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>
#include <String.h>
#include <ctype.h>

char* acronym(char *word);

int main(int argc,char **argv) {
    char phrases[8][100] = { " automatic teller machine","personal identification number","computer science","merry-go-round","All my Children","Trouble Assets Relief Program","--quite-- confusing - punctuation-","loner " };
    unsigned phrasesLength = sizeof(phrases) / sizeof(phrases[0]);
    for (unsigned i = 0; i < phrasesLength; i++) {
        printf("Phrase: %s\n",phrases[i]);
        printf("Acronym: %s\n\n",acronym(phrases[i]));
    }
    return 0;
}

char* acronym(char* word) {
    char wordCopy[500]; // wil hold a copy of word. Make large enough to avoid overflow
    unsigned wordLength = strlen(word);

    /* To use a function to copy word into wordCopy,you could do
       wordCopY[i] = '\0';
       strcpy(wordCopy,word);
    */
    // Here's how to do the copy manually
    for (unsigned i = 0; i < wordLength + 1; i++)
        wordCopY[i] = word[i];
    
    // wordCopy is now a copy of word

    unsigned indexWordCopy = 0; // start at first character of phrase
    unsigned indexResult = 0;   // start at first character of word
                                // this will override the characters that were
                                // there previously

    // iterate through word copy character by character. Store the acronym in word
    // which right now contains the original phrase
    while (!isalpha(wordCopY[indexWordCopy]))
        indexWordCopy++;
    word[indexResult++] = toupper(wordCopY[indexWordCopy++]);
    word[indexResult] = '\0';

    while (indexWordCopy < wordLength) {
        if (isalpha(wordCopY[indexWordCopy]) && !isalpha(wordCopY[indexWordCopy - 1])) {
            word[indexResult++] = toupper(wordCopY[indexWordCopy]);
            word[indexResult] = '\0';
        }
        indexWordCopy++;
    }
    return word;
}

输出

Phrase:  automatic teller machine
Acronym: ATM

Phrase: personal identification number
Acronym: PIN

Phrase: computer science
Acronym: CS

Phrase: merry-go-round
Acronym: MGR

Phrase: All my Children
Acronym: AMC

Phrase: Troubled Assets Relief Program
Acronym: TARP

Phrase: --quite-- confusing - punctuation-
Acronym: QCP

Phrase:  loner
Acronym: L