package Question3_3;
import java.util.ArrayList;
public class SetOfStacks {
ArrayList<Stack> stacks = new ArrayList<Stack>();
public int capacity;
public SetOfStacks(int capacity) {
this.capacity = capacity;
}
public Stack getLastStack() {
if (stacks.size() == 0) {
return null;
}
return stacks.get(stacks.size() - 1);
}
public void push(int v) {
Stack last = getLastStack();
if (last != null && !last.isFull()) { // add to last
last.push(v);
} else { // must create new stack
Stack stack = new Stack(capacity);
stack.push(v);
stacks.add(stack);
}
}
public int pop() {
Stack last = getLastStack();
int v = last.pop();
if (last.size == 0) {
stacks.remove(stacks.size() - 1);
}
return v;
}
public int popAt(int index) {
return leftShift(index, true);
}
public int leftShift(int index, boolean removeTop) {
Stack stack = stacks.get(index);
int removed_item;
if (removeTop) removed_item = stack.pop();
else removed_item = stack.removeBottom();
if (stack.isEmpty()) {
stacks.remove(index);
} else if (stacks.size() > index + 1) {
int v = leftShift(index + 1, false);
stack.push(v);
}
return removed_item;
}
public boolean isEmpty() {
Stack last = getLastStack();
return last == null || last.isEmpty();
}
}