[002] delete_duplication_of_linked_list

[Description] Given a unsort linked list, delete all the duplication from them, no temporary space permission.

[Thought] Set two points, from head to tail, scaning all linked list. O(n^2).

[Implementation] C code:

#include<stdio.h>

typedef struct linkedList
{
        int data;
        struct linkedList* next;
} llist;

llist** delDupli(llist **head)
{
        // two point, t1 for target, t2 for mover.
        llist *t1, *t2;
        t1=t2=*head;
        while(t1->next != NULL)
        {
                // ajust t2 from t1!
                t2=t1;
                while(t2->next != NULL)
                {
                        // check if they are the same
                        if(t2->next->data == t1->data)
                        {
                                // move t2->next; note: no memory free here.
                                t2->next=t2->next->next;
                        }
                        // after move out node, check if t2 is already the last one.
                        if(t2->next != NULL)
                        {
                                t2=t2->next;
                        }
                }
                t1=t1->next;
        }
        return head;
}

int addValue(llist **head, int val)
{

        llist *pnode;
        llist *t=*head;
        // apply memory for linked list.
        pnode=(llist*)malloc(sizeof(llist));
        if(NULL==pnode)
        {
                return 0;
        }
        pnode->data=val;
        pnode->next=NULL;
        // first node
        if(NULL==*head)
        {
                *head=pnode;
                return 1;
        }
        // move temp point to the last node
        while(t->next != NULL)
        {
                t=t->next;
        }
        t->next=pnode;
        return 1;
}

// out put data, be careful about the first node.
int printList(llist **head)
{
        llist *t=*head;
        printf("%d, ",t->data);
        while(t->next != NULL)
        {
                t=t->next;
                printf("%d, ",t->data);
        }
        printf("\n");
        return 1;
}

int main()
{
        int a[]={2,3,5,6,8,2,4,6,8,9,2,5,2};
        llist *head=NULL;
        int i;

        for(i=0;i<(sizeof(a)/sizeof(a[0]));i++)
        {
//              printf("a[i]:%d\n",a[i]);
                addValue(&head,a[i]);
//              printList(&head);
        }
        printf("Initial linked list:\n");
        printList(&head);
        printf("After deleting:\n");
        printList(delDupli(&head));
}