|
| 1 | +from typing import Any, List |
| 2 | + |
| 3 | + |
| 4 | +class Queue: |
| 5 | + |
| 6 | + def __init__(self) -> None: |
| 7 | + self.queue:List[Any] = [] |
| 8 | + |
| 9 | + def size(self) -> int: |
| 10 | + return len(self.queue) |
| 11 | + |
| 12 | + def is_empty(self) -> bool: |
| 13 | + return len(self.queue) == 0 |
| 14 | + |
| 15 | + def enqueue(self, item:Any) -> None: |
| 16 | + self.queue.insert(0, item) |
| 17 | + |
| 18 | + def dequeue(self) -> Any: |
| 19 | + if self.is_empty(): |
| 20 | + raise Exception('Queue is empty') |
| 21 | + return self.queue.pop() |
| 22 | + |
| 23 | + |
| 24 | + |
| 25 | +class Stack: |
| 26 | + |
| 27 | + def __init__(self): |
| 28 | + self.input: Queue = Queue() |
| 29 | + self.output:Queue = Queue() |
| 30 | + |
| 31 | + |
| 32 | + def push(self, x: Any) -> None: |
| 33 | + self.input.enqueue(x) |
| 34 | + |
| 35 | + |
| 36 | + def pop(self) -> Any: |
| 37 | + if self.input.is_empty(): |
| 38 | + raise Exception('Queue is empty') |
| 39 | + |
| 40 | + while self.input.size() > 1: |
| 41 | + self.output.enqueue(self.input.dequeue()) |
| 42 | + |
| 43 | + item:Any = self.input.dequeue() |
| 44 | + |
| 45 | + while not self.output.is_empty(): |
| 46 | + self.input.enqueue(self.output.dequeue()) |
| 47 | + |
| 48 | + return item |
| 49 | + |
| 50 | + |
| 51 | + def peek(self) -> Any: |
| 52 | + if self.input.is_empty(): |
| 53 | + raise Exception('Queue is empty') |
| 54 | + |
| 55 | + while self.input.size() > 1: |
| 56 | + self.output.enqueue(self.input.dequeue()) |
| 57 | + |
| 58 | + item:Any = self.input.dequeue() |
| 59 | + self.output.enqueue(item) |
| 60 | + |
| 61 | + while not self.output.is_empty(): |
| 62 | + self.input.enqueue(self.output.dequeue()) |
| 63 | + return item |
| 64 | + |
| 65 | + |
| 66 | + def is_empty(self) -> bool: |
| 67 | + return self.input.is_empty() |
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