Queue via Stacks

Author: nickolasteixeira

Python/chapter03/3.4 - Queue via Stacks/Nick.py

@@ -0,0 +1,123 @@
+#!/usr/bin/python3
+'''Queue via Stacks: Implement a MyQueue class
+which implements a queue using two stacks.'''
+import unittest
+
+
+class Stack:
+    def __init__(self):
+        self.stack = []
+        self.min = None
+
+    def getMin(self):
+        return self.min
+
+    def pop(self):
+        if not self.length:
+            print('No stack to pop')
+            return
+
+        item = self.stack.pop()
+
+        if item == self.min:
+            if self.length() > 0:
+                self.findMin()
+            else:
+                self.min = None
+        return item
+
+    def findMin(self):
+        self.min = self.stack[0]
+        for x in self.stack:
+            if x < self.min:
+                self.min = x
+
+    def length(self):
+        return len(self.stack)
+
+    def push(self, value):
+        if not self.min:
+            self.min = value
+        elif value < self.min:
+            self.min = value
+
+        self.stack.append(value)
+
+    def peek(self):
+        if not self.length:
+            print('No stack to peek')
+            return
+        return self.stack[-1]
+
+    def printStack(self):
+        if not self.length:
+            print('No stack to peeek')
+            return
+
+        print("Top of stack\n _ ")
+        for x in self.stack[::-1]:
+            print('|', x, '|')
+            print('|', '_', '|')
+
+
+class MyQueue:
+    def __init__(self):
+        self.newStack = Stack()
+        self.oldStack = Stack()
+
+    def push(self, value):
+        self.newStack.push(value)
+
+    def pop(self):
+        self.rotate()
+        if self.oldStack.length() == 0:
+            print('Nothing to pop in this queue')
+            return
+        return self.oldStack.pop()
+
+    def peek(self):
+        self.rotate()
+        if self.oldStack.length() == 0:
+            print('Nothing to peek in this queue')
+            return
+        return self.oldStack.peek()
+
+    def rotate(self):
+        if (self.oldStack.length() == 0):
+            while not self.newStack.length() == 0:
+                self.oldStack.push(self.newStack.pop())
+
+    def printQueue(self):
+        self.rotate()
+        for x in self.oldStack.stack[::-1]:
+            print('Item in Queue -->', x)
+
+        for x in self.newStack.stack:
+            print('Item in Queue -->', x)
+
+
+class Test(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        pass
+
+    @classmethod
+    def tearDownClass(cls):
+        pass
+
+    def test1(self):
+        arr = [2, 5, 7, 10, 3, 10, -1, -100]
+        print(arr)
+        q = MyQueue()
+        for x in arr:
+            q.push(x)
+
+        q.printQueue()
+        print('First in Queue --> Popped', q.pop())
+        print('Second in Queue --> Popped', q.pop())
+        q.printQueue()
+        print('Let\'s take a peek -->', q.peek())
+
+
+if __name__ == '__main__':
+    unittest.main()