Stack: Pop

Task: Remove the top value from the stack

class Stack {    private Object[] a = new Object[N];    private int top = -1;        // -1 means empty     void push(Object v) { a[++top] = v; }    Object pop()        { return a[top--]; }    Object peek()       { return a[top]; }    int size()          { return top + 1; }}

What you are watching

Pop removes the value on top and returns it. C was pushed last and so leaves first - last in, first out - and B, which was underneath it, becomes reachable for the first time since C arrived. Nothing else moves: the values below keep their positions, and only the top pointer steps down.