我正在尝试在C
中打乱链表。我已经考虑通过在整个列表中运行来做到这一点,对于每个对象,我将尝试随机化索引并在它们之间交换。看起来代码可以工作,但是在我运行代码一段时间后,列表的一部分似乎消失了,有时我被踢出了应用程序。
这是代码:
void main() {
Song* head = createSong(1, "aaaa", "aaaa");
Song* song2 = createSong(2, "bbbb", "bbbb");
Song* song3 = createSong(3, "cccc", "cccc");
addSongToTheEndOfTheList(head, song2);
addSongToTheEndOfTheList(head, song3);
printPlaylist(head);
shuffleList(head);
printPlaylist(head);
//freePlaylist(head);
}
int countList(Song* head) {
Song* currentSong = head;
int i = 0;
if (currentSong)
{
while (currentSong->next)
{
currentSong = currentSong->next;
i++;
}
i++;
}
return i;
}
void swapSong(Song* head,Song* Source, int id) {
Song* tempSong = (Song*)malloc(sizeof(Song));
Song* currentSong = head;
while(currentSong && currentSong->id != id){
currentSong = currentSong->next;
}
if (currentSong) {
tempSong->id = currentSong->id;
tempSong->name = currentSong->name;
tempSong->artist = currentSong->artist;
tempSong->next = currentSong->next;
currentSong->id = Source->id;
currentSong->name = Source->name;
currentSong->artist = Source->artist;
currentSong->next = Source->next;
Source->id = tempSong->id;
Source->name = tempSong->name;
Source->artist = tempSong->artist;
Source->next = tempSong->next;
free(tempSong);
}
else {
printf("The list is empty.");
}
}
void shuffleList(Song* head) {
Song* currentSong = head;
int listLength = countList(head);
int randNum;
srand(time(NULL));
if (currentSong) {
for (int i = 1; currentSong;i++) {
swapSong(head, currentSong, rand()%listLength+1);
currentSong = currentSong->next;
}
}
else {
printf("The list is empty.");
}
}
完整的代码在这里:https://pastebin.com/fSS3rrTv
希望你能帮我弄清楚。谢谢!
错误在于swapSong
。有两种可能的方法可以交换列表中的元素:
- 要么交换数据,不要触摸指针
next
- 或者您不触摸数据添加更改指针
前者对于内部数据很少的单链表更简单(这是您的用例(,后者更适合双链表。
这里只需将swapSong
更改为:
void swapSong(Song* head,Song* Source, int id) {
Song* tempSong = (Song*)malloc(sizeof(Song));
Song* currentSong = head;
while(currentSong && currentSong->id != id){
currentSong = currentSong->next;
}
if (currentSong) {
tempSong->id = currentSong->id;
tempSong->name = currentSong->name;
tempSong->artist = currentSong->artist;
//tempSong->next = currentSong->next;
currentSong->id = Source->id;
currentSong->name = Source->name;
currentSong->artist = Source->artist;
//currentSong->next = Source->next;
Source->id = tempSong->id;
Source->name = tempSong->name;
Source->artist = tempSong->artist;
//Source->next = tempSong->next;
free(tempSong);
}
else {
printf("The list is empty.");
}
}
顺便说一句,在结构Song
中,id
被声明为int *
,而它被用作int
。更改为以下内容以删除某些警告:
typedef struct Song {
int id;
char* name;
char* artist;
struct Song* next;
}Song;
正如@500-InternalServerError所注意到的,您无需在swapSong
中分配任何内容:只需使用本地结构:
void swapSong(Song* head,Song* Source, int id) {
Song* currentSong = head;
while(currentSong && currentSong->id != id){
currentSong = currentSong->next;
}
if (currentSong) {
Song tempSong = *currentSong;
currentSong->id = Source->id;
currentSong->name = Source->name;
currentSong->artist = Source->artist;
Source->id = tempSong.id;
Source->name = tempSong.name;
Source->artist = tempSong.artist;
}
else {
printf("The list is empty.");
}
}