Design-2

Explain your approach in three sentences only at top of your code

Problem 1: (https://leetcode.com/problems/implement-queue-using-stacks/)

// Time Complexity : o(1) // Space Complexity : o(n) // Did this code successfully run on Leetcode : yes // Any problem you faced while coding this : no

// Your code here along with comments explaining your approach class MyQueue:

def __init__(self):
    # self.counter = 0
    self.main_stack = []
    self.buffer_stack = []

def push(self, x: int) -> None:
    self.main_stack.append(x)

def pop(self) -> int:
    self.transfer_to_buffer()
    return self.buffer_stack.pop()

def peek(self) -> int:
    self.transfer_to_buffer()
    return self.buffer_stack[-1]

def empty(self) -> bool:
    return not self.main_stack and not self.buffer_stack

def transfer_to_buffer(self):
    if not self.buffer_stack:
        while self.main_stack:
            self.buffer_stack.append(self.main_stack.pop())

Problem 2:

Design Hashmap (https://leetcode.com/problems/design-hashmap/) // Time Complexity : O(1) // Space Complexity : O(n) // Did this code successfully run on Leetcode : yes // Any problem you faced while coding this : no

class MyHashMap: class Node: def init(self, key, value): self.key = key self.value = value self.next = None

def __init__(self):
    self.size = 10000
    self.table = [None for _ in range(self.size)]

def hash(self, value):
    return value % self.size   

def put(self, key: int, value: int) -> None:
    # hash the key
    index = self.hash(key)
    # is there a node? : init dummy 
    if self.table[index] is None: self.table[index] = self.Node(-1, -1)

    prev = self._find(self.table[index], key)

    if prev.next: 
        prev.next.value = value
    else:
        prev.next = self.Node(key, value)
    
def get(self, key: int) -> int:
    index = self.hash(key)
    if self.table[index] is None: 
        return -1
    
    prev = self._find(self.table[index], key)

    if prev.next: 
        return prev.next.value
    return -1

def remove(self, key: int) -> None:
    index = self.hash(key)
    if self.table[index] is None: 
        return
    
    prev = self._find(self.table[index], key)
    if prev.next:
        prev.next = prev.next.next

def _find(self,head,key):
    prev = head
    curr = head.next
    while curr and curr.key != key:
        prev = curr
        curr = curr.next
    return prev