修改字符指针字符串数组 （char * string[]）

问：

我一直在给一个...有趣。。。任务。我被要求使用指针修改字符数组。

我知道：

*char = “某物”;是文本，无法修改。

char[] = “某物”;可以修改

但是呢：

main.c
------

static char* stringlist01[] = 
{
    "thiy iy a ytring",
    "this is also a string, unlike the first string",
    "another one, not a great one, and not really like the last two.",
    "a third string!",
    NULL,
};

int main()
{
    int ret = 9999;

    printf("////TEST ONE////\n\n");

    ret = changeLetterInString(stringlist01[0]);
    printf("Return is: %d\n\n", ret);

    printf("Stringlist01[0] is now: %s\n", stringlist01[0]);
}

和

changeLetterInString.c
----------------------

int changeLetterInString(char *sentence)
{    
    if (sentence != NULL)
    {
        // TODO
        // Need to change "thiy iy a ytring"
        // into "this is a string"
        // and save into same location so
        // main.c can see it.
    }

    success = 0;    // 0 is Good
    return success;
}

到目前为止，我已经尝试过：

    for (char* p = sentence; *p; ++p)
    {
        if (*p == 'y')
        {
            *p = 's';
        }
    }

我试过：

sentence[0] = 't'
sentence[1] = 'h'
sentence[2] = 'i'
sentence[3] = 's'   // and so on...

但两者都不起作用。

任何帮助和/或见解将不胜感激。