design-2

design-hashmap.py

@@ -0,0 +1,48 @@
+# time O(1)
+# space O(n)
+
+class Node:
+    def __init__(self, key=-1,val=-1, next=None):
+        self.key=key
+        self.val=val
+        self.next = next
+
+class MyHashMap:
+# key  | value
+# 100  | 1
+# 1100 | 2
+# 100 % 1000 = 100
+# 1100 %1000 = 100
+# key | value
+# 100 | (100,1)->(1100,2)
+    def __init__(self):
+        self.map = [Node() for i in range(1000)]
+
+    def hash(self,key):
+    	return key % len(self.map)
+
+    def put(self, key: int, value: int) -> None:
+    	cur = self.map[self.hash(key)]
+    	while cur.next:
+    		if cur.next.key == key:
+    			cur.next.val = value
+    			return
+    		cur = cur.next
+    	cur.next = Node(key,value)
+
+    def get(self, key: int) -> int:
+    	cur = self.map[self.hash(key)]
+    	while cur:
+    		if cur.key == key:
+    			return cur.val
+    		cur = cur.next 
+
+    	return -1
+
+    def remove(self, key: int) -> None:
+    	cur = self.map[self.hash(key)]
+    	while cur and cur.next:
+    		if cur.next.key == key:
+    			cur.next = cur.next.next
+    			return
+    		cur = cur.next 

queue-using-stacks.py

@@ -0,0 +1,39 @@
+# O(n) time
+# O(n) space
+
+class MyQueue:
+
+    def __init__(self):
+        self.inStack = [] # stores all newly pushed elements
+        self.outStack=[] # used for popping and peeking elements in fifo order
+
+    def push(self, x: int) -> None:
+        self.inStack.append(x)
+
+    def pop(self) -> int:
+        if not self.outStack:
+            while self.inStack:
+                self.outStack.append(self.inStack.pop())
+
+        return self.outStack.pop()
+
+    def peek(self) -> int:
+        if not self.outStack:
+            while self.inStack:
+                self.outStack.append(self.inStack.pop())
+
+        return self.outStack[-1]
+
+    def empty(self) -> bool:
+        if len(self.inStack)==0 and len(self.outStack)==0:
+            return True
+        else:
+            return False
+
+
+# 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()