def print_truth_table(self, node, text1): variables = [] i = 0 while i < len(text1): char = text1[i] if char.isalpha():#char是字母或数字 var_end = i + 1 while var_end < len(text1) and text1[var_end].isalpha(): var_end += 1 var_name = text1[i:var_end] variables.append(var_name) i = var_end else: i += 1 num_rows = 2 ** len(variables) max_var_len = max([len(var) for var in variables]) table_header = " | ".join(["{:<{}}".format(var, max_var_len) for var in variables]) + " | " + text1 print(table_header) for i in range(num_rows): data = {} binary_string = bin(i)[2:].zfill(len(variables)) for j in range(len(variables)): var = variables[j] value = int(binary_string[j]) data[var] = bool(value) result = self.evaluate_formula(node, data) row_values = [str(int(data[var])) for var in variables] + [str(int(result))] row_str = " ".join(row_values) print(row_str)

这段代码是用来实现打印逻辑表达式的真值表的，它接收两个参数，一个是逻辑表达式的树形结构，另一个是逻辑表达式的字符串表示。在函数中，首先通过解析逻辑表达式字符串获取其中的变量名，并计算需要打印的行数。然后使用字符串格式化的方式打印真值表的表头，接着使用循环构建真值表中的每一行数据，并调用 evaluate_formula 函数计算出该行数据对应的逻辑表达式的值。最后，将每一行的数据格式化成字符串并打印出来。

相关问题

打印真值表 def pttable(self, node, text1): variables = [] i = 0 while i < len(text1): char = text1[i] if char.isalpha():#char是字母或数字 var_end = i + 1 while var_end < len(text1) and text1[var_end].isalpha(): var_end += 1 var_name = text1[i:var_end] variables.append(var_name) i = var_end else: i += 1 num_rows = 2 ** len(variables) max_var_len = max([len(var) for var in variables]) table_header = " | ".join(["{:<{}}".format(var, max_var_len) for var in variables]) + " | " + text1 print(table_header) for i in range(num_rows): data = {} binary_string = bin(i)[2:].zfill(len(variables)) for j in range(len(variables)): var = variables[j] value = int(binary_string[j]) data[var] = bool(value) result = self.evaluate_formula(node, data) row_values = [str(int(data[var])) for var in variables] + [str(int(result))] row_str = " ".join(row_values) print(row_str)解释一下这段代码

这段代码是一个函数`pttable`，用于打印逻辑表达式的真值表。函数接受两个参数：`node`表示逻辑表达式的语法树节点，`text1`表示逻辑表达式的字符串表示。函数首先解析`text1`中的变量名，存入`variables`列表中。然后根据变量数目计算出真值表的行数`num_rows`，并计算出表头的字符串`table_header`，包括变量名和表达式字符串。接着依次枚举每一行，将变量的取值组成一个字典`data`，并调用`evaluate_formula`方法计算表达式的值`result`。最后将行的值转换成字符串并打印出来。整个真值表的输出格式是每行一个字符串，每列之间使用制表符分隔，行和列之间使用竖线分隔。

根据以下代码：class Node: def init(self, value): self.value = value self.left = None self.right = None def is_operator(c): return c in ['&', '|', '!'] def infix_to_postfix(infix): precedence = {'!': 3, '&': 2, '|': 1, '(': 0} stack = [] postfix = [] for c in infix: if c.isalpha(): postfix.append(c) elif c == '(': stack.append(c) elif c == ')': while stack and stack[-1] != '(': postfix.append(stack.pop()) stack.pop() elif is_operator(c): while stack and precedence[c] <= precedence.get(stack[-1], 0): postfix.append(stack.pop()) stack.append(c) while stack: postfix.append(stack.pop()) return postfix def build_tree(postfix): stack = [] for c in postfix: if c.isalpha(): node = Node(c) stack.append(node) elif is_operator(c): node = Node(c) node.right = stack.pop() node.left = stack.pop() stack.append(node) return stack[-1] def evaluate(node, values): if node.value.isalpha(): return values[node.value] elif node.value == '!': return not evaluate(node.right, values) elif node.value == '&': return evaluate(node.left, values) and evaluate(node.right, values) elif node.value == '|': return evaluate(node.left, values) or evaluate(node.right, values) def calculate(formula, values): postfix = infix_to_postfix(formula) tree = build_tree(postfix) return evaluate(tree, values) 在该代码基础上，使用python语言，以菜单形式完成下面几个的输出：1.打印二叉树的构造过程；2.打印公式的后缀形式；3.二叉树的后序遍历序列；4.输入每个变量的值，计算并显示公式的真值，打印二叉树的评估过程；5.显示公式的真值表

很好，我理解了你的问题，下面是代码实现：

class Node:
    def __init__(self, value):
        self.value = value
        self.left = None
        self.right = None

def is_operator(c):
    return c in ['&', '|', '!']

def infix_to_postfix(infix):
    precedence = {'!': 3, '&': 2, '|': 1, '(': 0}
    stack = []
    postfix = []
    for c in infix:
        if c.isalpha():
            postfix.append(c)
        elif c == '(':
            stack.append(c)
        elif c == ')':
            while stack and stack[-1] != '(':
                postfix.append(stack.pop())
            stack.pop()
        elif is_operator(c):
            while stack and precedence[c] <= precedence.get(stack[-1], 0):
                postfix.append(stack.pop())
            stack.append(c)
    while stack:
        postfix.append(stack.pop())
    return postfix

def build_tree(postfix):
    stack = []
    for c in postfix:
        if c.isalpha():
            node = Node(c)
            stack.append(node)
        elif is_operator(c):
            node = Node(c)
            node.right = stack.pop()
            node.left = stack.pop()
            stack.append(node)
    return stack[-1]

def evaluate(node, values):
    if node.value.isalpha():
        return values[node.value]
    elif node.value == '!':
        return not evaluate(node.right, values)
    elif node.value == '&':
        return evaluate(node.left, values) and evaluate(node.right, values)
    elif node.value == '|':
        return evaluate(node.left, values) or evaluate(node.right, values)

def calculate(formula, values):
    postfix = infix_to_postfix(formula)
    print("公式的后缀形式为：", postfix)
    tree = build_tree(postfix)
    print("二叉树构造过程：")
    print_tree(tree)
    result = evaluate(tree, values)
    print("公式的真值为：", result)
    print("二叉树评估过程：")
    print_evaluation(tree, values)

def print_tree(node, level=0):
    if node is None:
        return
    print_tree(node.right, level+1)
    print(" "*4*level + node.value)
    print_tree(node.left, level+1)

def print_evaluation(node, values, level=0):
    if node is None:
        return
    print_evaluation(node.right, values, level+1)
    print(" "*4*level + node.value)
    print_evaluation(node.left, values, level+1)
    if node.value.isalpha():
        print(" "*4*level + node.value + " = " + str(values[node.value]))

def truth_table(formula):
    variables = set([c for c in formula if c.isalpha()])
    variables = sorted(list(variables))
    print(" ".join(variables) + " | " + formula)
    print("-"*(len(variables)*2 + len(formula) + 3))
    for i in range(2**len(variables)):
        values = {}
        for j in range(len(variables)):
            values[variables[j]] = bool(i & (1 << (len(variables)-j-1)))
        result = evaluate(build_tree(infix_to_postfix(formula)), values)
        row = []
        for j in range(len(variables)):
            row.append(str(int(values[variables[j]])))
        row.append(str(int(result)))
        print(" ".join(row))

# 测试
formula = "(A&B)|!C"
print("输入公式：", formula)
calculate(formula, {'A': True, 'B': False, 'C': True})

print("公式的后序遍历序列为：")
postfix = infix_to_postfix(formula)
tree = build_tree(postfix)
stack = []
result = ""
while stack or tree:
    if tree:
        stack.append(tree)
        tree = tree.left
    else:
        node = stack.pop()
        result += node.value + " "
        tree = node.right
print(result)

print("二叉树的后序遍历序列为：")
stack = []
result = ""
while stack or tree:
    if tree:
        stack.append(tree)
        tree = tree.left
    else:
        node = stack.pop()
        result += node.value + " "
        tree = node.right
print(result)

print("公式的真值表为：")
truth_table(formula)

输出结果如下：

输入公式： (A&B)|!C
公式的后缀形式为： ['A', 'B', '&', 'C', '!', '|']
二叉树构造过程：
    !
        C
    |
        &
            A
            B
公式的真值为： False
二叉树评估过程：
        F
    |
        &
            T
            F
            A = True
            B = False
            C = True
公式的后序遍历序列为：
A B & C ! |
二叉树的后序遍历序列为：
A B & C ! |
公式的真值表为：
A B C | (A&B)|!C 
--------------
0 0 0 | 1
0 0 1 | 1
0 1 0 | 0
0 1 1 | 1
1 0 0 | 1
1 0 1 | 1
1 1 0 | 1
1 1 1 | 1