script:doc['gcList'].value script_stack:["doc['gcList'].value"]

这个错误是由于 `gcList` 字段在某些文档中可能不存在，导致脚本执行时出现了空指针异常。为了避免这个错误，可以在脚本中添加判断语句，例如：

if (doc.containsKey('gcList') && doc['gcList'].size() > 0) {
    return doc['gcList'].value;
} else {
    return null;
}

在这个脚本中，首先判断了 `gcList` 字段是否存在，并且数组的大小是否大于0。如果满足条件，则返回 `gcList` 数组的值，否则返回 `null`。

请注意，在 Elasticsearch 中，如果脚本返回了 `null`，则会将对应的文档排在最后。如果需要将缺失字段的文档排在最前面，则可以将 `return null;` 改为 `return 0;`。

相关问题

这是上题的代码：def infix_to_postfix(expression): precedence = {'!': 3, '&': 2, '|': 1, '(': 0} op_stack = [] postfix_list = [] token_list = expression.split() for token in token_list: if token.isalnum(): postfix_list.append(token) elif token == '(': op_stack.append(token) elif token == ')': top_token = op_stack.pop() while top_token != '(': postfix_list.append(top_token) top_token = op_stack.pop() else: # operator while op_stack and precedence[op_stack[-1]] >= precedence[token]: postfix_list.append(op_stack.pop()) op_stack.append(token) while op_stack: postfix_list.append(op_stack.pop()) return ' '.join(postfix_list) class Node: def __init__(self, value): self.value = value self.left_child = None self.right_child = None def build_expression_tree(postfix_expr): operator_stack = [] token_list = postfix_expr.split() for token in token_list: if token.isalnum(): node = Node(token) operator_stack.append(node) else: right_node = operator_stack.pop() left_node = operator_stack.pop() node = Node(token) node.left_child = left_node node.right_child = right_node operator_stack.append(node) return operator_stack.pop() def evaluate_expression_tree(node, variable_values): if node.value.isalnum(): return variable_values[node.value] else: left_value = evaluate_expression_tree(node.left_child, variable_values) right_value = evaluate_expression_tree(node.right_child, variable_values) if node.value == '!': return not left_value elif node.value == '&': return left_value and right_value elif node.value == '|': return left_value or right_value expression = "!a & (b | c)" postfix_expression = infix_to_postfix(expression) expression_tree = build_expression_tree(postfix_expression) variable_values = {'a': True, 'b': False, 'c': True} result = evaluate_expression_tree(expression_tree, variable_values) print(result)

好的，感谢提供代码。以下是针对你的问题的解答：

1. 打印二叉树构造过程

在 build_expression_tree 函数中，operator_stack 列表存储了构建二叉树的过程。我们可以在函数中添加打印语句来查看二叉树构建过程。

代码如下：

def build_expression_tree(postfix_expr):
    operator_stack = []
    token_list = postfix_expr.split()

    for token in token_list:
        if token.isalnum():
            node = Node(token)
            operator_stack.append(node)
        else:
            right_node = operator_stack.pop()
            left_node = operator_stack.pop()
            node = Node(token)
            node.left_child = left_node
            node.right_child = right_node
            operator_stack.append(node)
        
        # 打印二叉树构建过程
        print([i.value for i in operator_stack])

    return operator_stack.pop()

在运行 build_expression_tree 函数时，将会打印出二叉树构建过程。

2. 打印后缀表达式和二叉树后序遍历序列

在函数 infix_to_postfix 中，postfix_list 列表存储了后缀表达式。我们可以在函数返回后缀表达式的同时，打印出后缀表达式。

代码如下：

def infix_to_postfix(expression):
    precedence = {'!': 3, '&': 2, '|': 1, '(': 0}
    op_stack = []
    postfix_list = []
    token_list = expression.split()

    for token in token_list:
        if token.isalnum():
            postfix_list.append(token)
        elif token == '(':
            op_stack.append(token)
        elif token == ')':
            top_token = op_stack.pop()
            while top_token != '(':
                postfix_list.append(top_token)
                top_token = op_stack.pop()
        else:
            # operator
            while op_stack and precedence[op_stack[-1]] >= precedence[token]:
                postfix_list.append(op_stack.pop())
            op_stack.append(token)

    while op_stack:
        postfix_list.append(op_stack.pop())

    # 打印后缀表达式
    print(f"后缀表达式：{' '.join(postfix_list)}")

    return ' '.join(postfix_list)


def build_expression_tree(postfix_expr):
    operator_stack = []
    token_list = postfix_expr.split()

    for token in token_list:
        if token.isalnum():
            node = Node(token)
            operator_stack.append(node)
        else:
            right_node = operator_stack.pop()
            left_node = operator_stack.pop()
            node = Node(token)
            node.left_child = left_node
            node.right_child = right_node
            operator_stack.append(node)
        
        # 打印二叉树构建过程
        print([i.value for i in operator_stack])

    return operator_stack.pop()

expression = "!a & (b | c)"
postfix_expression = infix_to_postfix(expression)
expression_tree = build_expression_tree(postfix_expression)

# 打印二叉树后序遍历序列
print("二叉树后序遍历序列：", end="")
def postorder(node):
    if node:
        postorder(node.left_child)
        postorder(node.right_child)
        print(node.value, end=" ")
postorder(expression_tree)
print()

在运行程序时，将会先打印出后缀表达式，然后是构建二叉树的过程，最后打印出二叉树的后序遍历序列。

3. 打印二叉树评估过程

在 evaluate_expression_tree 函数中，我们可以添加打印语句来查看二叉树评估的过程。

代码如下：

def evaluate_expression_tree(node, variable_values):
    if node.value.isalnum():
        return variable_values[node.value]
    else:
        left_value = evaluate_expression_tree(node.left_child, variable_values)
        right_value = evaluate_expression_tree(node.right_child, variable_values)
        if node.value == '!':
            result = not left_value
        elif node.value == '&':
            result = left_value and right_value
        elif node.value == '|':
            result = left_value or right_value

        # 打印二叉树评估过程
        print(f"节点 {node.value} 的值为 {result}")

        return result

expression = "!a & (b | c)"
postfix_expression = infix_to_postfix(expression)
expression_tree = build_expression_tree(postfix_expression)
variable_values = {'a': True, 'b': False, 'c': True}
result = evaluate_expression_tree(expression_tree, variable_values)
print(result)

在运行程序时，将会先打印出后缀表达式，然后是构建二叉树的过程，接着会打印出二叉树评估的过程。

4. 显示公式真值表

可以通过遍历变量的所有取值，来计算表达式的真值表。

代码如下：

expression = "!a & (b | c)"
postfix_expression = infix_to_postfix(expression)
expression_tree = build_expression_tree(postfix_expression)

# 遍历变量的所有可能取值
variable_values = {'a': True, 'b': False, 'c': True}
variable_names = list(variable_values.keys())
print(" ".join(variable_names), expression)

for i in range(2**len(variable_names)):
    values = [bool(int(x)) for x in bin(i)[2:].zfill(len(variable_names))]
    variable_values = dict(zip(variable_names, values))
    result = evaluate_expression_tree(expression_tree, variable_values)
    print(" ".join([str(int(x)) for x in values]), int(result))
    

在运行程序时，将会先打印出后缀表达式，然后是构建二叉树的过程，接着会打印出真值表。

优化这段代码：class Stack: def __init__(self): self.stack=[] def push(self,element): self.stack.append(element) def pop(self): if len(self.stack)>0: return self.stack.pop() def get_top(self): if len(self.stack)>0: return self.stack(-1) else : return None def is_empty(self): return len(self.stack)==0 def brace_match(s): match={')':'(',']':'[','}':'{'} stack=Stack() for ch in s: if ch in {'(','[','{'}: stack.push(ch) else: if stack.is_empty(): return False elif stack.get_top() == match[ch]: stack.pop() else: return False if stack.is_empty(): return True else: return False # match={')':'(',']':'[','}':'{'} # print(match[')']) print(brace_match('()'))

优化后的代码如下：

class Stack:
def __init__(self):
self.stack = []

def push(self, element):
self.stack.append(element)

def pop(self):
if self.stack:
return self.stack.pop()

def get_top(self):
if self.stack:
return self.stack[-1]

def is_empty(self):
return not self.stack

def brace_match(s):
match = {')': '(', ']': '[', '}': '{'}
stack = Stack()
for ch in s:
if ch in {'(', '[', '{'}:
stack.push(ch)
else:
if stack.is_empty() or stack.get_top() != match[ch]:
return False
stack.pop()
return stack.is_empty()