The deletion of the first element in the case of a single linked list without knowing the head node

First, take a look at the deletion of element I in the single-linked list:

Status listdelete_l (linklist &l,int i,elemtype &e) {

in the single-linked table L of the lead node, delete the element I , and return its value by E

p=l;j=0;

while (p->next&&j<i-1) {// finds The first node and points p to its predecessor

p=p->next;

++j;

}

if (! ( P->next) | |  J<I-1) return ERROR; The deletion of the location is unreasonable

q=p->next;p->next=q->next; Delete and Release nodes

E=q->data;free (q);

return OK;

}

For example, delete the 3rd element C in the single-linked list L, i.e. delete the 4th node:

1) At the beginning, the P pointer points to the head node,j=0;

2) Executes the loop statement, when j=2 ,p points to the third node, the loop ends;

3) q=p->next;p->next=q->next; Delete and release nodes;

The deletion of C nodes is implemented.

Second, the single-linked list of the first node in the case of the deletion of the first element:

For example, the deletion of the B-node, the first only to know the pointer to the B-node q, because it is a single-linked list, cannot get to the precursor pointer, so the above method can not be deleted.

You can use the following statement to implement the deletion of the Q node:

q->data=q->next->data;

q->next=q->next->next;

At this point, theL single-linked list becomes:

Although the C node is deleted, it copies the data in C to B, which is equivalent to deleting the b node.

Note, however, that this deletion method cannot delete a node at the end of the table because there is no other node in the back that can be replaced.

The deletion of the first element in the case of a single linked list without knowing the head node