How to Solve Dinner Plate Stacks Problem

You have an infinite number of stacks arranged in a row and numbered (left to right) from 0, each of the stacks has the same maximum capacity. Implement the DinnerPlates class: DinnerPlates(int capacity) Initializes the object with the maximum capacity of the stacks capacity. void push(int val) Pushes the given integer val into the leftmost stack with a size less than capacity. int pop() Returns the value at the top of the rightmost non-empty stack and removes it from that stack, and returns -1 if all the stacks are empty. int popAtStack(int index) Returns the value at the top of the stack with the given index index and removes it from that stack or returns -1 if the stack with that given index is empty.