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”]

[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 
                                         ﹈ ﹈ ﹈ 
D.popAtStack(0);    // Returns 2. The stacks are now:   4 
                                                  1 3 5 
                                                 ﹈ ﹈ ﹈ 
D.push(20);         // The stacks are now: 20 4 
                                           1 3 5 
                                          ﹈ ﹈ ﹈ 
D.push(21);         // The stacks are now: 20 4 21 
                                           1 3 5 
                                           ﹈ ﹈ ﹈ 
D.popAtStack(0);    // Returns 20. The stacks are now: 4 21 
                                                      1 3 5 
                                                     ﹈ ﹈ ﹈ 
D.popAtStack(2);    // Returns 21. The stacks are now: 4 
                                                    1 3 5 
                                                   ﹈ ﹈ ﹈ 
D.pop()             // Returns 5. The stacks are now: 4 
                                                    1 3 
                                                    ﹈ ﹈ 
D.pop()             // Returns 4. The stacks are now: 1 3 
                                                    ﹈ ﹈ 
D.pop()             // Returns 3. The stacks are now: 1 
                                                     ﹈ 
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 Summary

Constructors

Constructor and Description
DinnerPlates(int capacity)

Method Summary

Modifier and Type	Method and Description
int	pop()
int	popAtStack(int index)
void	push(int val)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DinnerPlates

public DinnerPlates(int capacity)

Method Detail

push

public void push(int val)

pop

public int pop()

popAtStack

public int popAtStack(int index)