c语言写自己的字符串处理函数

一个大学的c语言实验题目，要求都在上面了，其中三个函数都写出来了，就差一个stringGetWord函数始终玩不明白，感觉陷进去了。帮忙的话，可以指出我哪里错了，错的太多不好说也可以你自己直接写出来。谢谢！

#include "strings.h"
#include 
#include 

static void printAllWords(char const* string, size_t numberofWords)
{
    char buffer[256];
    for (size_t i = 0; i < numberofWords; i++)
    {
        stringPrint(stringGetWord(string, buffer, i));
        putchar(', ');
    }
    puts("");
}

int main() {

    const char* strings[] = {
       "Dollar#",
       "One dollar#",
       "    Two    dollars    #",
       "   Three dollars here       #",
       "Four dollars in all   #" };
    
    char firstBuffer[8]; // Just able to hold the first string   
    char secondBuffer[16];
    char thirdBuffer[32];
    char fourthBuffer[512]; // big enough
    char fifthBuffer[512];

    stringCopy(strings[0], firstBuffer); stringPrint(firstBuffer); printf("\n");
    stringCopy(strings[1], secondBuffer); stringPrint(secondBuffer); printf("\n");
    stringCopy(strings[2], thirdBuffer); stringPrint(thirdBuffer); printf("\n");
    stringCopy(strings[3], fourthBuffer); stringPrint(fourthBuffer); printf("\n");
    stringCopy(strings[4], fifthBuffer); stringPrint(fifthBuffer); printf("\n");

   printf("First: %zu == %zu\n", stringLength(strings[0]), stringLength(firstBuffer));  //某些编译系统下此处需进行修改，下同
    printf("Second: %zu == %zu\n", stringLength(strings[1]), stringLength(secondBuffer));
    printf("Third: %zu == %zu\n", stringLength(strings[2]), stringLength(thirdBuffer));
    printf("Fourth: %zu == %zu\n", stringLength(strings[3]), stringLength(fourthBuffer));
    printf("Fifth: %zu == %zu\n", stringLength(strings[4]), stringLength(fifthBuffer));

    printf("-------\n");
    printf("getWord tests\n");

    printf("%s",stringGetWord(strings[1], fourthBuffer, 1));
/*
    printAllWords(firstBuffer, 1);
    printAllWords(secondBuffer, 2);
    printAllWords(thirdBuffer, 2);
    printAllWords(fourthBuffer, 3);
    printAllWords(fifthBuffer, 4);
     printf("-------\n");
    printf("Checking what happens if a word can't be found\n");

    char buf[1];     //某些编译系统下此处需要修改程序才能运行
    buf[0] = '$';

    char* ptr = stringGetWord(firstBuffer, buf, 1);  //1.某些编译系统下此处需要修改程序才能运行; 2. 请深刻理解此函数、改变实参值并运行程序加深理解
    if (ptr != NULL)
        printf("Function did not return NULL...\n");
    if (buf[0] != '$')
        printf("Buf has been modified...\n");
*/
}

strings.cpp

#include
#include 
void stringPrint(const char* str)
{
    const char* p=str;
    for (; (*p) != '#'; p++)
        printf("%c", *p);
}
void stringCopy(const char* str, char* dest)
{
    int i;
    const char* p1 = str;
    char* p2 = dest;
    for (i = 0; *(p1 + i) != '#'; i++)
        *(p2 + i) = *(p1 + i);
    *(p2 + i) = '#';
}
size_t stringLength(const char* str)
{
    size_t i, num = 0;
    const char* p = str;
    for (i = 0; *(p + i) != '#'; i++)
        num++;
    return(num);
}

char* stringGetWord(const char* str, char* dest, size_t index)//
{
    int num,word = 0;
    char* p0=dest;
    /*for (num = 0; *str != '#'; str++)
    {
        if (*str == ' ')
            word = 1;
        else if (word == 0)
        {
            word = 1;
            num++;
        }
    }                //先算字符串单词个数用来判断
    if (num == 0 || index > num - 1)
        return NULL;
    else {}*/
        stringCopy(str, dest);
        for (num=0; num<= index; )
        {
            if (*str == ' ')
                word = 0;
            else if (word == 0)
            {
                word = 1;
                num++;
                p0 = dest;        //把指向第index个的地址储存下来，因为待会dest要去寻找后面的空格或#，地址要变
            }
        }
        for (; *dest != ' ' && *dest != '#'; dest++);
        *dest = '#';
        dest = p0;
            return(dest);
    
}/**/

strings.h

```c
#ifndef  _C_STRINGS_H
#define  _C_STRINGS_H

#include 
/* All functions in this header operate on strings that use '#' as their terminating character, not \0.
 * In addition, you can assume that all buffers are big enough (but not bigger!) for the operation. */


 /* This function works just like strlen(), except the terminating character is #, not \0 */
size_t stringLength(const char* str);


/* This function works just like strcpy(), except the terminating character is #, not \0 and the parameters are in different order.
 * (The function copies the string pointed to by str to the memory area pointed to by dest.)
 * Oh, and unlike strcpy, this function  return nothing. */
void stringCopy(const char* str, char* dest);

/* This function is used to select a certain word from a string.
 * String is delimited by the space character ' ' into words. In other words, Word is a sequence of characters without any space characters.
 * The first word has index 0.
 * The function writes the selected word to the string pointed to by "dest".
 * If the index is out of bounds (the string does not have enough words), then the function does not modify dest and the return value is NULL.
 * If the operation was successful, "dest" pointer is returned (pointing to the first character of the word).
 */
char* stringGetWord(const char* str, char* dest, size_t index);//

/* This function prints the string to the standard output. The function does not print
 * any additional characters besides those present in the string. */
void stringPrint(const char* str);
#endif