updated progress

queue.py

+# queue code from http://knuth.luther.edu/~leekent/CS2Plus/chap4/chap4.html
+
+class Queue:
+    def __init__(self):
+        self.items = []
+        self.frontIdx = 0
+
+    def __compress(self):
+        newitems = []
+        for i in range(self.frontIdx,len(self.items)):
+            newitems.append(self.items[i])
+
+        self.items = newitems
+        self.frontIdx = 0
+
+    def dequeue(self):
+        if self.isEmpty():
+            raise RuntimeError("Attempt to dequeue an empty queue")
+
+        # When queue is half full, compress it. This 
+        # achieves an amortized complexity of O(1) while
+        # not letting the list continue to grow unchecked. 
+        if self.frontIdx * 2 > len(self.items):
+            self.__compress()
+
+        item = self.items[self.frontIdx]
+        self.frontIdx += 1
+        return item
+
+    def enqueue(self,item):
+        self.items.append(item)
+
+    def front(self):
+        if self.isEmpty():
+            raise RuntimeError("Attempt to access front of empty queue")
+
+        return self.items[self.frontIdx]
+
+
+    def isEmpty(self):
+        return self.frontIdx == len(self.items)
+
+    def clear(self):
+        self.items = []
+        self.frontIdx = 0
+
+def main():
+    q = Queue()
+    items = list(range(10))
+    items2 = []
+
+    for k in items:
+        q.enqueue(k)
+
+    if q.front() == 0:
+        print("Test 1 Passed")
+    else:
+        print("Test 1 Failed")
+
+    while not q.isEmpty():
+        items2.append(q.dequeue())
+
+    if items2 != items:
+        print("Test 2 Failed")
+    else:
+        print("Test 2 Passed")
+
+    for k in items:
+        q.enqueue(k)   
+
+    items2 = []
+
+    while not q.isEmpty():
+        items2.append(q.dequeue())  
+
+    if items2 != items:
+        print("Test 3 Failed")
+    else:
+        print("Test 3 Passed")
+
+    try:
+        q.dequeue()
+        print("Test 4 Failed")
+
+    except RuntimeError:
+        print("Test 4 Passed")
+    except:
+        print("Test 4 Failed")
+
+    try:
+        q.front()
+        print("Test 5 Failed")
+
+    except RuntimeError:
+        print("Test 5 Passed")
+    except:
+        print("Test 5 Failed")  
+
+if __name__=="__main__":
+    main()
\ No newline at end of file

tree.py

+# base tree code from http://knuth.luther.edu/~leekent/CS2Plus/chap6/chap6.html
+# changed this code to allow for variable functions, and change infix expressions to postfix
+
+import queue
+
+class TimesNode:
+    def __init__(self, left, right):
+        self.left = left
+        self.right = right
+        
+    def eval(self):  
+        return self.left.eval() * self.right.eval()
+    
+    def inorder(self):
+        return "(" + self.left.inorder() + " * " + self.right.inorder() + ")" 
+    
+class PlusNode:
+    def __init__(self, left, right):
+        self.left = left
+        self.right = right
+        
+    def eval(self):
+        return self.left.eval() + self.right.eval()
+    
+    
+    def inorder(self):
+        return "(" + self.left.inorder() + " + " + self.right.inorder() + ")"  
+
+class MinusNode:
+    def __init__(self,left, right):
+        self.left = left
+        self.right = right
+
+    def eval(self):
+        return self.left.eval() - self.right.eval()
+
+    def inorder(self):
+        return "(" + self.left.inorder() + "-" + self.right.inorder() + ")"
+
+class NumNode:
+    def __init__(self, num):
+        self.num = num
+        
+    def eval(self):
+        return self.num
+    
+    def inorder(self):
+        return str(self.num)
+
+def check_if_variables(x, y):
+    if 'x' in x and 'x' in y:
+        return "both_vars"
+    elif 'x' in x or 'x' in y:
+        return "one_var"
+    else:
+        return "both_const"
+
+def E(q):
+    if q.isEmpty():
+        raise ValueError("Invalid Prefix Expression")
+    
+    token = q.dequeue()
+
+    if token == "+":
+        return PlusNode(E(q),E(q))
+    
+    if token == "*":
+        return TimesNode(E(q),E(q))
+
+    if token == "-":
+        return MinusNode(E(q), E(q))
+    
+    try:
+        output = NumNode(float(token))
+    except:
+        print("Not a valid operation, need variables of like terms")
+        output = NumNode(float(0))
+    return output
+
+OPERATORS = set(['+', '-', '*', '/', '(', ')'])
+PRIORITY = {'+':1, '-':1, '*':2, '/':2}
+
+def infix_to_prefix(formula):
+    op_stack = []
+    exp_stack = []
+    for ch in formula.split():
+        if not ch in OPERATORS:
+            exp_stack.append(ch)
+        elif ch == '(':
+            op_stack.append(ch)
+        elif ch == ')':
+            while op_stack[-1] != '(':
+                op = op_stack.pop()
+                a = exp_stack.pop()
+                b = exp_stack.pop()
+                exp_stack.append( op+b+a )
+            op_stack.pop() # pop '('
+        else:
+            while op_stack and op_stack[-1] != '(' and PRIORITY[ch] <= PRIORITY[op_stack[-1]]:
+                op = op_stack.pop()
+                a = exp_stack.pop()
+                b = exp_stack.pop()
+                exp_stack.append( op+" "+b+" "+a )
+            op_stack.append(ch)
+    
+    # leftover
+    while op_stack:
+        op = op_stack.pop()
+        a = exp_stack.pop()
+        b = exp_stack.pop()
+        exp_stack.append( op+" "+b+" "+a )
+    print exp_stack[-1]
+    return exp_stack[-1]
+
+  
+def eval_tree(expression):
+    x = NumNode(5)
+    y = NumNode(4)
+    p = PlusNode(x,y)
+    t = TimesNode(p, NumNode(6))
+    root = PlusNode(t, NumNode(3))
+    
+    print(root.eval())
+    print(root.inorder())
+    
+    #x = input("Please enter a prefix expression: ")
+    x = infix_to_prefix(expression)
+
+    lst = x.split()
+    q = queue.Queue()
+    
+    for token in lst:
+        q.enqueue(token)
+        
+    root = E(q)
+    
+    print(root.eval())
+    print(root.inorder())
+
+    #print(infix_to_prefix("3 + 4 - 6"))
+
+def split_equation(equation):
+    expressions = equation.split("=")
+    return expressions
+
+def main():
+    exp = split_equation("3 * 4 - 6=0")
+    eval_tree(exp[0])
+        
+    
+if __name__ == "__main__":
+    main()
\ No newline at end of file