Untitled

#include <stdio.h>
#include <stdlib.h>

struct SongType {
    int data;
    struct SongType *prev;
    struct SongType *next;
};
typedef struct SongType Song;
int CUR_SONG=0;

Song *createSong(int val) {
    Song *newSong = (Song *)malloc(sizeof(Song));
    newSong -> data = val;
    newSong -> prev = NULL;
    newSong -> next = NULL;
    return newSong;
}

Song *addSong(Song *head, int val) {
    Song *newSong = createSong(val);
    if(head == NULL) {
        return newSong;
    }
    Song *cur = head;
    while(cur -> next != NULL) {
        cur = cur -> next;
    }
    cur -> next = newSong;
    newSong -> prev = cur;
    return newSong;
}

Song *createPlaylist () {
    int n;
    scanf("%d", &n);
    Song *head = NULL;
    for(int i=0; i<n; i++) {
        int x;
        scanf("%d",&x);
        if(head == NULL) {
            head = addSong(head,x);
        } else {
            addSong(head,x);
        }
    }
    return head;
}

Song *currentPlaying(Song *head) {
    if(CUR_SONG == 0) {
        CUR_SONG = head->data;
        return head;
    }
    Song *cur = head;
    while(cur -> data != CUR_SONG) {
        cur = cur ->next;
    }
    return cur;
}

Song *previousSong(Song *head) {
    Song *curPlaying = currentPlaying(head);
    Song *cur = head;
    if(curPlaying->prev == NULL) {
        return curPlaying;
    }
    while(cur -> data != curPlaying -> data) {
        cur = cur->next;
    }
    cur = cur->prev;
    CUR_SONG = cur->data;
    return cur;
}

Song *nextSong(Song *head) {
    Song *curPlaying = currentPlaying(head);
    Song *cur = head;
    if(curPlaying -> next == NULL) {
        return curPlaying;
    }
    while(cur -> data != curPlaying -> data) {
        cur = cur -> next;
    }
    cur =  cur->next;
    CUR_SONG = cur -> data;
    return cur;
}

int main() {
    Song  *playlist = createPlaylist();
    while(1) {
        int x;
        scanf("%d", &x);

        if(x==1) {
            int ns;
            scanf("%d", &ns);
            addSong(playlist,ns);
        } else if(x==2) {
            printf("%d\n",currentPlaying(playlist)->data);
        } else if(x==3) { 
            nextSong(playlist);
        } else if(x==4) {
            previousSong(playlist);
        } else if(x==5) {
            break;
        } else {
            printf("INVALID OPERATION\n");
        }
    }
    return 0;
}