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| class StackOfPlates {
private final List<Stack<Integer>> stackList;
private final int cap;
private int lastNotFullStackIndex;
public StackOfPlates(int cap) {
this.stackList = new ArrayList<>();
this.cap = cap;
this.lastNotFullStackIndex = -1;
}
public void push(int val) {
if (cap <= 0) {
return;
}
if (lastNotFullStackIndex == -1) {
stackList.add(new Stack<>());
lastNotFullStackIndex++;
}
Stack<Integer> stack = stackList.get(lastNotFullStackIndex);
if (stack.size() == cap) {
stackList.add(new Stack<>());
lastNotFullStackIndex++;
}
stackList.get(lastNotFullStackIndex).push(val);
}
public int pop() {
for (int i = stackList.size() - 1; i >= 0; i--) {
Stack<Integer> stack = stackList.get(i);
if (!stack.isEmpty()) {
int val = stack.pop();
if (stack.isEmpty()) {
lastNotFullStackIndex--;
}
return val;
}
}
return -1;
}
public int popAt(int index) {
for (int i = index; i < stackList.size(); i++) {
Stack<Integer> stack = stackList.get(i);
if (!stack.isEmpty()) {
int val = stack.pop();
if (stack.isEmpty()) {
lastNotFullStackIndex--;
}
return val;
}
}
return -1;
}
}
|