CSE 202 Pseudo Codes 2

Insert ans Delete operation on a Singly Linked List

Each Item on a Singly Linked List is formed with two fields, Info (which contains the data for the node) and Next (which is a pointer to the next Item). A pointer 'head' points the start of the linked list, and in case the linked list is empty, head has the value 'null'. Pseudo-codes for insertion and deletion at nth position is shown below:

Insert Procedure

Insert ( head, n, item )
    if n = 1 then
        temp := new Node;
        Info[temp] := item, Next[temp] = head;
        head = temp;
        return;
    ptr := head, pos := 1;
    repeat while pos + 1 < n and Next[ptr] != null
        ptr := Next[ptr], pos = pos + 1;
    temp := new Node;
    Info[temp] = item, Next[temp] = Next[ptr];
    Next[ptr] = temp;
    return;

Delete Procedure

Delete ( head, n )
    if head = null then return;
    if n = 1 then
        temp := head, head := Next[head];
        free temp;
        return;
    ptr := head, pos := 1;
    repeat while pos + 1 < n and Next[ptr] != null
        ptr := Next[ptr], pos := pos + 1;
    if Next[ptr] = null then return
    temp := Next[ptr], Next[ptr] = Next[temp];
    free temp;
    return;

Both of them handle all the possible cases on a singly linked list.