Stack & Queue

⚠️ This post was created when I was in high school and is no longer maintained.

1. Stack Pseudocode

algorithm IsEmpty(S):
    if S.top == 0 then
        return True
    else 
        return False

algorithm Pop(S):
    if IsEmpty(S) then
        throw StackUnderflow
    else
        S.top = S.top - 1
        return S[S.top+1]
        
algorithm Push(S, x):
    if S.top == S.size then
        throw StackOverflow
    else 
        S.top += 1
        S[S.top] = x

2. Queue

algorithm Enqueue(Q, x):
    if (Q.tail == Q.length and Q.head == 1) or
       (Q.head == Q.tail + 1) then
        throw QueueFullException

    Q[Q.tail] = x
    if Q.tail == Q.length --> wrap around
        Q.tail = 1
    else
        Q.tail += 1

algorithm Dequeue(Q):
    if Q.head == Q.tail then
        throw QueueEmptyException

    x = Q[Q.head]
    if Q.head == Q.length
        Q.head = 1
    else
        Q.head += 1
    return x