add Bag, Stack, Queue

Author: shellfly

algs4/bag.py

@@ -0,0 +1,47 @@
+
+"""
+Execution:    python bag < input.txt
+
+% more tobe.txt
+to be or not to - be - - that - - - is
+
+% python stack < tobe.txt
+to be or not to - be - - that - - - is
+"""
+
+from algs4.utils.linklist import Node, LinkIterator
+
+
+class Bag:
+
+    def __init__(self):
+        self.first = None
+        self.n = 0
+
+    def __str__(self):
+        return " ".join(i for i in self)
+
+    def __iter__(self):
+        return LinkIterator(self.first)
+
+    def size(self):
+        return self.n
+
+    def is_empty(self):
+        return self.first is None
+
+    def add(self, item):
+        oldfirst = self.first
+        self.first = Node(item, oldfirst)
+        self.n += 1
+
+
+if __name__ == '__main__':
+    import sys
+    for line in sys.stdin:
+        bag = Bag()
+        for item in line.split():
+            bag.add(item)
+        print("size of bag = ", bag.size())
+        for i in bag:
+            print(i)

algs4/queue.py

@@ -0,0 +1,64 @@
+"""
+Execution:    python queue < input.txt
+
+% more tobe.txt 
+to be or not to - be - - that - - - is
+
+% python queue < tobe.txt
+to be or not to be (2 left on queue)
+"""
+
+from algs4.utils.linklist import Node, LinkIterator
+
+
+class Queue:
+
+    def __init__(self):
+        self.first = None
+        self.last = None
+        self.n = 0
+
+    def __str__(self):
+        return " ".join(i for i in self)
+
+    def __iter__(self):
+        return LinkIterator(self.first)
+
+    def size(self):
+        return self.n
+
+    def is_empty(self):
+        return self.first is None
+
+    def enqueue(self, item):
+        oldlast = self.last
+        self.last = Node(item, None)
+        if self.is_empty():
+            self.first = self.last
+        else:
+            oldlast.next = self.last
+        self.n += 1
+
+    def dequeue(self):
+        if self.is_empty():
+            raise ValueError("Queue empty")
+        else:
+            item = self.first.item
+            self.first = self.first.next
+            if self.is_empty():
+                self.last = None
+            self.n -= 1
+            return item
+
+
+if __name__ == '__main__':
+    import sys
+
+    for line in sys.stdin:
+        queue = Queue()
+        for item in line.split():
+            if item != "-":
+                queue.enqueue(item)
+            elif not queue.is_empty():
+                print(queue.dequeue() + " ", end='')
+        print("(%d left on queue)" % queue.size())

algs4/stack.py

@@ -0,0 +1,57 @@
+"""
+Execution:    python stack < input.txt
+
+% more tobe.txt 
+to be or not to - be - - that - - - is
+
+% python stack < tobe.txt
+to be not that or be (2 left on stack)
+"""
+
+from algs4.utils.linklist import Node, LinkIterator
+
+
+class Stack:
+
+    def __init__(self):
+        self.first = None
+        self.n = 0
+
+    def __str__(self):
+        return " ".join(i for i in self)
+
+    def __iter__(self):
+        return LinkIterator(self.first)
+
+    def size(self):
+        return self.n
+
+    def is_empty(self):
+        return self.first is None
+
+    def push(self, item):
+        oldfirst = self.first
+        self.first = Node(item, oldfirst)
+        self.n += 1
+
+    def pop(self):
+        if self.is_empty():
+            raise ValueError("Stack underflow")
+        else:
+            item = self.first.item
+            self.first = self.first.next
+            self.n -= 1
+            return item
+
+
+if __name__ == '__main__':
+    import sys
+
+    for line in sys.stdin:
+        stack = Stack()
+        for item in line.split():
+            if item != "-":
+                stack.push(item)
+            elif not stack.is_empty():
+                print(stack.pop() + " ", end='')
+        print("(%d left on stack)" % stack.size())

algs4/utils/linklist.py

@@ -0,0 +1,19 @@
+class Node:
+
+    def __init__(self, item, nextItem):
+        self.item = item
+        self.next = nextItem
+
+
+class LinkIterator:
+
+    def __init__(self, current):
+        self.current = current
+
+    def __next__(self):
+        if self.current is None:
+            raise StopIteration()
+        else:
+            item = self.current.item
+            self.current = self.current.next
+            return item