Stacks
last-in, first-out (LIFO)
insertion operation: Push
deletion operation:Pop
If an empty stack is popped, then stack underflows
If top［S ］ exceeds n, then stack overflows.
Pseudo code of stack empty
STACK -EMPTY
if top[S]＝0
then return ture
else return false
PUSH(S, x)
top[S]←top [S ]+1
S[top[S]]←x
Pop(S)
if STACK-EMPTY(S)
then error "underflows"
else top[S] ←top[S]－1
return S[top[S]+1]
Each of the three stack operations takes Ο（1） tim.
Queue
First in, first out( FIFO)
Enqueue (Q, x )
Q[tail[Q]]←x
if tail[Q]=length[Q]
then tail[Q]←1
else tail[Q]←tail[Q]+1
Dequeue(Q)
x←Q[head[Q]]
if head[Q]=length [Q]
then head[Q]=1
else head[Q]←head[Q]+1
return x
Inserting into a linked list
LIST -Insert (L, x)
next [x ]←head [L]
if head [L]≠NIL
then prev [head [L ]]←x
head [L]←x
prev [x]←NIL
