Submit Design-2 PR

Exercise_1.py

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+# Implement Queue using Stacks
+# https://leetcode.com/problems/implement-queue-using-stacks/
+
+# Time complexity: O(1)
+# Space complexity: O(n)
+
+# uses an in stack for all incoming elements; when either peek or pop operation is called, then all elements from in stack is moved to out stack;
+# this way out stack will have the first element added
+
+class MyQueue:
+
+    def __init__(self):
+        self.in_st = []
+        self.out_st = []
+
+    def push(self, x: int) -> None:
+        self.in_st.append(x)
+
+    def pop(self) -> int:
+        if self.empty():
+            return -1
+
+        self.peek()
+        return self.out_st.pop()
+
+    def peek(self) -> int:
+        if self.empty():
+            return -1
+
+        if not self.out_st:
+            while self.in_st:
+                self.out_st.append(self.in_st.pop())
+
+        return self.out_st[-1]
+
+    def empty(self) -> bool:
+        return not self.in_st and not self.out_st
+
+
+# Your MyQueue object will be instantiated and called as such:
+# obj = MyQueue()
+# obj.push(x)
+# param_2 = obj.pop()
+# param_3 = obj.peek()
+# param_4 = obj.empty()

Exercise_2.py

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+# Design HashMap
+# https://leetcode.com/problems/design-hashmap/
+
+# Time complexity: O(1)
+# Space complexity: O(n)
+
+# Use hashing and linear chaining - use a larger bucket size to reduce the number of collisions and also make the traversal in the buckets tend to constant time lookup;
+# HashMap contains both a key and a value, hence a Node needs to be used instead of just one value.
+
+class Node:
+    def __init__(
+        self,
+        key: int = -1,
+        value: int = -1,
+        next_node: Node | None = None
+    ):
+        self.key = key
+        self.value = value
+        self.next = next_node
+
+
+class MyHashMap:
+
+    def __init__(self):
+        self.primary_buckets = 10000
+        self.storage = [Node() for _ in range(self.primary_buckets)]
+
+    def _get_hash(self, key: int) -> int:
+        return key % self.primary_buckets
+
+    def _get_prev(self, key: int) -> Node:
+        bucket_index = self._get_hash(key)
+        prev = self.storage[bucket_index]
+        curr = prev.next
+
+        while curr is not None and curr.key != key:
+            prev = curr
+            curr = curr.next
+
+        return prev
+
+    def put(self, key: int, value: int) -> None:
+        prev = self._get_prev(key)
+
+        if prev.next is not None:
+            prev.next.value = value
+        else:
+            prev.next = Node(key, value)
+
+    def get(self, key: int) -> int:
+        prev = self._get_prev(key)
+
+        if prev.next is None:
+            return -1
+
+        return prev.next.value
+
+    def remove(self, key: int) -> None:
+        prev = self._get_prev(key)
+
+        if prev.next is not None:
+            prev.next = prev.next.next
+
+
+# Your MyHashMap object will be instantiated and called as such:
+# obj = MyHashMap()
+# obj.put(key,value)
+# param_2 = obj.get(key)
+# obj.remove(key)