def parChecker(symbol_string):
"""
先写一个只有'()'类型的算法
@symbol_string: 要匹配的括号字符串
@return: 返回匹配结果,bool类型
"""
stack = Stack()
index = 0
balanced_flag = True # 两边括号数量平衡标识
while index < len(symbol_string) and balanced_flag:
symbol = symbol_string[index]
if symbol == '(':
stack.push(symbol)
else:
if stack.isEmpty():
balanced_flag = False
else:
stack.pop()
index += 1
if balanced_flag and stack.isEmpty():
balanced_flag = True
else:
balanced_flag = False
return balanced_flag
def infixToPostfix(infixExpr):
"""
中缀表达式转后缀表达式算法实现
@infixExpr: 中缀表达式,格式如:A + B * C,必须含空格,且操作数只包含A-Z 0-9其中的值
@return: 转换成功的后缀表达式
"""
# 记录操作符优先级
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
op_stack = Stack()
possible_str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
post_fix_lst = []
token_lst = infixExpr.split()
for token in token_lst:
# 如果单词是 操作数, 则直接添加到后缀表达式列表的末尾
if token in possible_str:
post_fix_lst.append(token)
# 如果单词是左'(', 则压入栈顶,标记下
elif token == '(':
op_stack.push(token)
# 如果单词是右')',则反复弹出栈顶操作符,加入到输出列表末尾,直到遇到左括号
elif token == ')':
top_token = op_stack.pop()
while top_token != '(':
post_fix_lst.append(top_token)
top_token = op_stack.pop()
# 如果单词是操作符, 则压入栈顶,
# 但在压之前, 要比较其与栈顶操作符的优先级
# 如果栈顶操作符的优先级高于它, 就要反复弹出栈顶操作符, 加入到输出列表末尾
# 直到栈顶操作符的优先级低于它
else:
# 注意条件prec[op_stack.peek()] >= prec[token], 不是 > ,是 >=,因为+- 或*/是同一级
while (not op_stack.isEmpty()) and (prec[op_stack.peek()] >=
prec[token]):
post_fix_lst.append(op_stack.pop())
op_stack.push(token)
# 扫描结束后,把opstack栈中的所有剩余操作符依次弹出,加入到输出列表末尾
# 把输出列表再用join()合并成后缀表达式字符串
while not op_stack.isEmpty():
post_fix_lst.append(op_stack.pop())
return " ".join(post_fix_lst)
def express_convert(text):
'''将中缀表达式转换成后缀表达式
看懂算法的前提是了解中缀表达式转换后缀表达式的过程；
明确表达式包含的元素：1）操作数，这里将操作数抽象为a-z，即26个小写字母集合；
2）操作符，+-*/，+-同等优先级，*/同等优先级并且优先级高于+-
3）小括号。小括号内的表达式要先算
示例：
a + b + c ==> ab+c+
a + b * c ==> abc*+
a * (b + c) ==> abc+*
a + (b + c) * d == > a b c + d * +
算法流程：
0）用result_list存储结果
1）遇操作数，将其append进result_list
2）遇操作符，如栈内无元素，入栈；
如栈内有元素，与栈顶元素比较优先级；比栈顶优先级高，则入栈，小于或等于，则弹出栈顶元素并append到result_list，再入
3）遇左括号，入栈；
4）遇右括号，不断弹出栈顶操作符，直至弹出左括号。
:param text: str, 中缀表达式
:return: str, 后缀表达式
'''
text = text.replace(' ', '')
result_list = []
stack = Stack()
priority = {'(': 1, '*': 2, '/': 2, '+': 3, '-': 3}
for i in text:
if i in 'abcdefghijklmnopqrstuvwxyz':
result_list.append(i)
elif i in '+-*/(':
if not stack.is_empty():
top_item = stack.get_top()
if top_item != '(' and priority[i] >= priority[top_item]:
item = stack.pop()
result_list.append(item)
stack.push(i)
# print(stack.get_items())
elif i in ')':
while True:
item = stack.pop()
if item == '(':
break
result_list.append(item)
while not stack.is_empty():
item = stack.pop()
result_list.append(item)
return ' '.join(result_list)
def par_checker(text):
'''
括号匹配，这里只考虑大、中、小括号。
算法思路很简单，从左到右遍历文本，左括入栈，遇右括出栈，出栈时检查匹配与否；遍历完检索栈内是否还有元素
:param text: 输入文本
:return: True or False
'''
result = True
stack = Stack()
left_par = '([{'
right_par = {')': '(', ']': '[', '}': '{'}
for i in text:
if i in left_par:
stack.push(i)
if i in right_par.keys():
if stack.is_empty():
result = False
break
pop_item = stack.pop()
if pop_item != right_par[i]:
result = False
break
if not stack.is_empty():
result = False
return result
def decimal_convert(num, convert_to=2):
'''将十进制数转换成其它进制数，以字符串返回
算法思路就是用十进制数除以N（进制），取余，直至结果为0。最后的余数为新进制数的最高位，符合栈的后进先出特点，故用栈存储余数。
:param num: int, 十进制数字
:param convert_to: int, 要转换的进制
:return: str， 转换后的数字
'''
if not num:
return '0'
stack = Stack()
# 这个技巧非常漂亮。将余数的数字与字母对应起来（十六进制场景）
ch = '0123456789ABCDEF'
while num // convert_to:
item = num % convert_to
num = num // convert_to
stack.push(item)
if num:
stack.push(num)
res = ''
while not stack.is_empty():
res += str(ch[stack.pop()])
return res
def parCheckerMore(symbol_string):
"""
通用括号匹配,支持 (, [, { 这三种
@symbol_string: 要匹配的括号字符串
@return: 返回匹配结果,bool类型
"""
stack = Stack()
index = 0
balanced_flag = True # 两边括号数量平衡标识
while index < len(symbol_string) and balanced_flag:
symbol = symbol_string[index]
# 判断左边括号类型需要调整
if symbol in '([{':
stack.push(symbol)
else:
if stack.isEmpty():
balanced_flag = False
else:
top = stack.pop()
# 栈中移除的括号要和进入栈的括号匹配类型
if not matches(top, symbol):
balanced_flag = False
index += 1
if balanced_flag and stack.isEmpty():
balanced_flag = True
else:
balanced_flag = False
return balanced_flag
def convert_to_base(self, base):
decimal = self.a
s = Stack()
while decimal > 0:
decimal, remender = divmod(decimal, base)
s.push(remender)
n = ""
while not s.isEmpty():
n += Digit.digits[s.pop()]
self.a = n
def postfixEval(postfixExpr):
"""
后缀表达式求值
@postfixExpr: 后缀表达式
@return: 计算结果
"""
token_lst = postfixExpr.split()
operand_stack = Stack()
for token in token_lst:
# 如果是操作数,则压入栈顶
if token in '123456789':
operand_stack.push(int(token))
# 否则取操作数开始计算
else:
# 栈的特性,后进先出
operand2 = operand_stack.pop()
operand1 = operand_stack.pop()
result = math_eval(token, operand1, operand2)
operand_stack.push(result)
return operand_stack.pop()
def divideBy2(decNumber):
"""
10进制数转2进制
@num: 需要转换的数
@return: 转换后的结果
"""
remainder_stack = Stack()
while decNumber > 0:
remainder = decNumber % 2
remainder_stack.push(remainder)
decNumber //= 2 # 整除
result = ''
while not remainder_stack.isEmpty():
result += str(remainder_stack.pop())
return result
class PreorderIteratorStack:
def __init__(self, root):
self.current = None
self.stack = Stack(1000)
self.stack.push(root)
def __iter__(self):
return self
def __next__(self):
if self.stack.is_empty():
raise StopIteration
current = self.stack.pop()
if current.right is not None:
self.stack.push(current.right)
if current.left is not None:
self.stack.push(current.left)
return current.item
def baseConvert(decNumber, base):
"""
10进制数转成任意16进制以下的数
@decNumber: 需要转换的数
@base: 进制
@return: 转换后的结果
"""
digits = '0123456789ABCDEF' # 定义数范围(最大16进制)
remainder_stack = Stack()
while decNumber > 0:
remainder = decNumber % base
remainder_stack.push(remainder)
decNumber //= base # 整除
result = ''
while not remainder_stack.isEmpty():
result += digits[remainder_stack.pop()]
return result
def dfs(gui, one_step=False):
starting_pos = gui.grid.head.get_node()
fringe = Stack()
# Fringe holds a list of tuples: (node position, move to get prev to current, cost)
fringe.push([(starting_pos, None, 0)])
path = []
visited = [starting_pos]
while not fringe.is_empty():
# Get the next one to be popped off the stack to search it's neighbor nodes (successors)
path = fringe.pop()
visited.append(path[-1][0])
if gui.grid.grid[path[-1][0][0]][path[-1][0][1]] == 3:
break
for neighbor in get_neighbors(gui, path[-1][0][0], path[-1][0][1]):
if neighbor[0] not in visited:
updated_path = copy.copy(path)
updated_path.append(neighbor)
fringe.push(updated_path)
if not fringe.is_empty():
move_set = []
while path:
temp = path.pop(0)
if temp[1] is not None:
move_set.append(temp[1])
if not one_step:
return move_set
else:
return [move_set[0]]
else:
no_dfs_move = go_furthest(gui)
if no_dfs_move:
return no_dfs_move
else:
no_moves_at_all = go_down()
return no_moves_at_all
queue.add(7)
print("the data structure is of size: " + str(queue.get_size()))
print(queue.remove())
print(queue.remove())
print(queue.remove())
print(queue.remove())
print("the data structure is of size: " + str(queue.get_size()))
print("\nTESTING STACK WITH ARRAYS\n")
stack = Stack("array")
stack.push(2)
stack.push(4)
stack.push(7)
print("the data structure is of size: " + str(stack.get_size()))
print(stack.pop())
print(stack.pop())
print(stack.pop())
print(stack.pop())
print("the data structure is of size: " + str(stack.get_size()))
print("\nTESTING QUEUE WITH LINKED_LIST\n")
queue = Queue("linked")
queue.add(2)
queue.add(4)
queue.add(7)
print("the data structure is of size: " + str(queue.get_size()))
print(queue.remove())
print(queue.remove())
print(queue.remove())