Implement queue using stack

hashset.py

@@ -0,0 +1,90 @@
+class Node(object):
+
+    def __init__(self, key):
+        self.key = key
+        self.next = None
+
+
+class MyHashSet(object):
+
+    def __init__(self):
+        """
+        Initialize your data structure here.
+        """
+        self.size = 1000
+        self.hashset = [None] * self.size
+
+
+    def hashing(self, key):
+        return key % self.size
+
+
+    def add(self, key):
+        """
+        :type key: int
+        :rtype: None
+        """
+        hashed = self.hashing(key)
+        if self.hashset[hashed]:
+            current = self.hashset[hashed]
+            while current:
+                if current.key == key:
+                    return
+                elif current.next is None:
+                    break
+                current = current.next
+            current.next = Node(key)
+        else:
+            self.hashset[hashed] = Node(key)
+
+    def remove(self, key):
+        """
+        :type key: int
+        :rtype: None
+        """
+        hashed = self.hashing(key)
+        if self.hashset[hashed]:
+            prev, current = self.hashset[hashed], self.hashset[hashed]
+            if not current:
+                return
+            elif current.key == key:
+                self.hashset[hashed] = current.next
+            else:
+                current = current.next
+                while current:
+                    if current.key == key:
+                        prev.next = current.next
+                        break
+                    prev, current = prev.next, current.next
+
+
+
+    def contains(self, key):
+        """
+        Returns true if this set contains the specified element
+        :type key: int
+        :rtype: bool
+        """
+        hashed = self.hashing(key)
+        if self.hashset[hashed]:
+            current = self.hashset[hashed]
+            while current:
+                if current.key == key:
+                    return True
+                current = current.next
+        return False
+
+
+hashSet = MyHashSet()
+hashSet.add(1)         
+hashSet.add(2)         
+print(hashSet.contains(1))
+# // returns true
+print(hashSet.contains(3))
+# // returns false (not found)
+hashSet.add(2)          
+print(hashSet.contains(2))
+# // returns true
+hashSet.remove(2)          
+print(hashSet.contains(2))
+# // returns false (already removed)

queueusingstack.py

@@ -0,0 +1,67 @@
+class MyQueue(object): 
+    def __init__(self):
+        self.mainstack=[]
+
+    def push(self, x):
+        #appending at the back
+        self.mainstack.append(x)
+
+    def pop(self):
+        #poppping the element from front 
+         #since it acts as a list last element would be -1 index
+        return self.mainstack.pop(-1)
+
+    def peek(self):
+        #returning the front element
+        #since it acts as a list last element would be -1 index
+        return self.mainstack[-1]
+
+    def empty(self):
+        return len(self.mainstack)==0
+    #here this is a python list even if its queue or stack it will be inserted from back and deleted from front.
+
+
+
+     # def __init__(self):
+#         self.mainstack=[]
+#         self.tmpstack=[]
+
+#     def push(self, x):
+#         while self.mainstack:
+#             self.tmpstack.append(self.mainstack.pop())
+#         self.tmpstack.append(x)
+#         while self.tmpstack:
+#             self.mainstack.append(self.tmpstack.pop())
+
+#     def pop(self):
+#         return self.mainstack.pop()
+
+
+#     def peek(self):
+#         return self.mainstack[-1]
+
+
+#     def empty(self):
+#         return len(self.mainstack)==0
+
+#     def __init__(self):
+#         self.mainstack=[]
+#         self.tmpstack=[]
+
+#     def push(self, x):
+#         while self.mainstack:
+#             self.tmpstack.append(self.mainstack.pop())
+#         self.tmpstack.append(x)
+#         while self.tmpstack:
+#             self.mainstack.append(self.tmpstack.pop())
+
+#     def pop(self):
+#         return self.mainstack.pop()
+
+
+#     def peek(self):
+#         return self.mainstack[-1]
+
+
+#     def empty(self):
+#         return len(self.mainstack)==0