Add pseudocodes to LinkedList.

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Oleksii Trekhleb 2018-08-13 10:38:19 +03:00
parent 02b70d95d6
commit f6c091bcb1

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@ -18,107 +18,123 @@ access, such as random access, is not feasible. Arrays
have better cache locality as compared to linked lists.
![Linked List](https://upload.wikimedia.org/wikipedia/commons/6/6d/Singly-linked-list.svg)
## Pseudocode
## Pseudocode for Basic Operations
### Insert
Add(value)
Pre: value is the value to add to the list
Post: value has been placed at the tail of the list
n ← node(value)
if head = ø
head ← n
tail ← n
else
tail.next ← n
tail ← n
end if
end Add
```text
Add(value)
Pre: value is the value to add to the list
Post: value has been placed at the tail of the list
n ← node(value)
if head = ø
head ← n
tail ← n
else
tail.next ← n
tail ← n
end if
end Add
```
### Search
Contains(head, value)
Pre: head is the head node in the list
value is the value to search for
Post: the item is either in the linked list, true; otherwise false
n ← head
while n = ø and n.value = value
n ← n.next
end while
if n = ø
return false
end if
return true
end Contains
```text
Contains(head, value)
Pre: head is the head node in the list
value is the value to search for
Post: the item is either in the linked list, true; otherwise false
n ← head
while n = ø and n.value = value
n ← n.next
end while
if n = ø
return false
end if
return true
end Contains
```
### Delete
Remove(head, value)
Pre: head is the head node in the list
Post: value is the value to remove from the list, true, otherwise false
if head = ø
return false
end if
n ← head
if n.value = value
if head = tail
head ← ø
tail ← ø
else
head ← head.next
end if
return true
end if
while n.next = ø and n.next.value = value
n ← n.next
end while
if n.next = ø
if n.next = tail
tail ← n
end if
n.next ← n.next.next
return true
end if
return false
end Remove
```text
Remove(head, value)
Pre: head is the head node in the list
Post: value is the value to remove from the list, true, otherwise false
if head = ø
return false
end if
n ← head
if n.value = value
if head = tail
head ← ø
tail ← ø
else
head ← head.next
end if
return true
end if
while n.next = ø and n.next.value = value
n ← n.next
end while
if n.next = ø
if n.next = tail
tail ← n
end if
n.next ← n.next.next
return true
end if
return false
end Remove
```
### Traverse
Traverse(head)
Pre: head is the head node in the list
Post: the items in the list have been traversed
n ← head
while n = 0
yield n.value
n ← n.next
end while
end Traverse
```text
Traverse(head)
Pre: head is the head node in the list
Post: the items in the list have been traversed
n ← head
while n = 0
yield n.value
n ← n.next
end while
end Traverse
```
### Traverse in Reverse
ReverseTraversal(head, tail)
Pre: head and tail belong to the same list
Post: the items in the list have been traversed in reverse order
if tail = ø
curr ← tail
while curr = head
prev ← head
while prev.next = curr
prev ← prev.next
end while
yield curr.value
curr ← prev
end while
yeild curr.value
end if
end ReverseTraversal
```text
ReverseTraversal(head, tail)
Pre: head and tail belong to the same list
Post: the items in the list have been traversed in reverse order
if tail = ø
curr ← tail
while curr = head
prev ← head
while prev.next = curr
prev ← prev.next
end while
yield curr.value
curr ← prev
end while
yeild curr.value
end if
end ReverseTraversal
```
## Big *O*
## Complexities
### Time Complexity
Access: *O*(*n*) \
Search: *O*(*n*) \
Insert: *O*(1) \
Delete: *O*(1)
| Access | Search | Insertion | Deletion |
| :-------: | :-------: | :-------: | :-------: |
| O(n) | O(n) | O(1) | O(1) |
### Space Complexity
*O*(*n*)
O(n)
## References