Package g1101_1200.s1172_dinner_plate_stacks

Class DinnerPlates

java.lang.Object
g1101_1200.s1172_dinner_plate_stacks.DinnerPlates
public class DinnerPlates extends Object
1172 - Dinner Plate Stacks.

Hard

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.

Example 1:

Input

[“DinnerPlates”, “push”, “push”, “push”, “push”, “push”, “popAtStack”, “push”, “push”, “popAtStack”, “popAtStack”, “pop”, “pop”, “pop”, “pop”, “pop”]

[[2], [1], [2], [3], [4], [5], [0], [20], [21], [0], [2], [], [], [], [], []]

Output: [null, null, null, null, null, null, 2, null, null, 20, 21, 5, 4, 3, 1, -1]

Explanation:

 DinnerPlates D = DinnerPlates(2); // Initialize with capacity = 2
 D.push(1); 
 D.push(2); 
 D.push(3); 
 D.push(4); 
 D.push(5);          // The stacks are now: 2 4 
                                           1 3 5 
                                           \ufe48 \ufe48 \ufe48 
 D.popAtStack(0);    // Returns 2. The stacks are now:   4 
                                                    1 3 5 
                                                   \ufe48 \ufe48 \ufe48 
 D.push(20);         // The stacks are now: 20 4 
                                             1 3 5 
                                            \ufe48 \ufe48 \ufe48 
 D.push(21);         // The stacks are now: 20 4 21 
                                             1 3 5 
                                             \ufe48 \ufe48 \ufe48 
 D.popAtStack(0);    // Returns 20. The stacks are now: 4 21 
                                                        1 3 5 
                                                       \ufe48 \ufe48 \ufe48 
 D.popAtStack(2);    // Returns 21. The stacks are now: 4 
                                                      1 3 5 
                                                     \ufe48 \ufe48 \ufe48 
 D.pop()             // Returns 5. The stacks are now: 4 
                                                      1 3 
                                                      \ufe48 \ufe48 
 D.pop()             // Returns 4. The stacks are now: 1 3 
                                                      \ufe48 \ufe48 
 D.pop()             // Returns 3. The stacks are now: 1 
                                                       \ufe48 
 D.pop()             // Returns 1. There are no stacks. 
 D.pop()             // Returns -1. There are still no stacks.

Constraints:

  • 1 <= capacity <= 2 * 104
  • 1 <= val <= 2 * 104
  • 0 <= index <= 105
  • At most 2 * 105 calls will be made to push, pop, and popAtStack.

  • Constructor Details

    • DinnerPlates

      public DinnerPlates(int capacity)

  • Method Details

    • push

      public void push(int val)

    • pop

      public int pop()

    • popAtStack

      public int popAtStack(int index)