python---自己来打通节点，链表，栈，应用

但，，

没有调试通过。

思路是对的，立此存照。

关键就是用链表完全实现列表的功能，

替换了就应该OK的。

# coding = utf-8

# 节点初始化
class Node:
    def __init__(self, init_data):
        self.data = init_data
        self.next = None

    def get_data(self):
        return self.data

    def get_next(self):
        return self.next

    def set_data(self, new_data):
        self.data = new_data

    def set_next(self, new_next):
        self.next = new_next

# 实现列表方法
class UnorderedList:
    def __init__(self):
        # 链表类本身不包含任何节点对象。
        # 它只包含对链接结构中第一个节点的单个引用。
        self.head = None

    def is_empty(self)->bool:
        return self.head is None

    # 加到链表第一项
    def add(self, item):
        temp = Node(item)
        temp.set_next(self.head)
        self.head = temp

    # 加到链表最后一项
    def append(self, item):
        if self.head is None:
            self.add(item)
        else:
            temp = Node(item)
            current = self.head
            previous = None
            while current is not None:
                previous = current
                current = current.get_next()
            previous.set_next(temp)

    # 这个动作和append一样
    def push(self, item):
        self.append(item)

    # 删除链表节点时，需要使用previous保存前一个节点
    def remove(self, item):
        current = self.head
        previous = None
        found = False
        while not found and current is not None:
            if current.get_data() == item:
                found = True
            else:
                previous = current
                current = current.get_next()
        if not found:
            raise Exception("not found.")
        if previous is None:
            self.head = current.get_next()
        else:
            previous.set_next(current.get_next())

    # 经典循环链表节点，并设置哨兵位
    def search(self, item):
        current = self.head
        found = False
        while current is not None and not found:
            if current.get_data() == item:
                found = True
            else:
                current = current.get_next()
        return found

    def size(self):
        current = self.head
        count = 0
        while current is not None:
            count += 1
            current = current.get_next()
        return count

    def index(self, item):
        found = False
        count = 0
        current = self.head
        while current is not None and not found:
            count += 1
            if current.get_data() == item:
                found = True
            else:
                current = current.get_next()
        if not found:
            raise Exception("not found.")
        return count

    def insert(self, pos, item):
        if self.head is None:
            raise Exception("not init")
        elif pos > self.size():
            raise Exception("pos is too large")
        else:
            temp = Node(item)
            current = self.head
            previous = None
            for i in range(pos):
                previous = current
                current = current.get_next()
            temp.set_next(current)
            previous.set_next(temp)

    def pop(self):
        current = self.head
        previous = None
        for i in range(self.size()-1):
            previous = current
            current = current.get_next()
        pop_value = current.get_data()
        previous.set_next(None)
        return pop_value

    def peek(self):
        current = self.head
        previous = None
        while current is not None:
            previous = current
            current = current.get_next()
        return previous.get_data()

    def pop_pos(self, pos):
        current = self.head
        previous = None
        for i in range(pos):
            previous = current
            current = current.get_next()
        pop_value = current.get_data()
        previous.set_next(current.get_next())
        return pop_value

    def show(self):
        current = self.head
        tmp = ''
        while current is not None:
            current = current.get_next()
            tmp += current.get_data()
        return tmp

'''
my_list = UnorderedList()
my_list.add(31)
my_list.add(77)
my_list.add(17)
my_list.add(93)
my_list.add(26)
my_list.add(54)
my_list.add(68)
my_list.append(100)
my_list.append(110)
my_list.insert(2, 57)
print(my_list.pop(), '=========pop===')
print(my_list.pop_pos(5), '=========pop_pos===')
my_list.show()
print(my_list.peek(), '=========peek===')
print(my_list.size())
print(my_list.search(68))
try:
    my_list.remove(310)
except Exception as error:
    print(error)

try:
    print(my_list.index(54))
except Exception as error:
    print(error)
my_list.show()
'''

class Stack:
    def __init__(self):
        self.items = UnorderedList()

    # 是否为空
    def is_empty(self):
        return self.items.is_empty()

    # 进栈
    def push(self, item):
        self.items.append(item)

    # 出栈
    def pop(self):
        return self.items.pop()

    # 返回栈顶值，不改变栈
    def peek(self):
        return self.items.peek()

    # 返回栈长度
    def size(self):
        return self.items.size()

def infix_to_postfix(infix_expr):
    prec = dict()
    prec["*"] = 3
    prec["/"] = 3
    prec["+"] = 2
    prec["-"] = 2
    prec["("] = 1
    prec[")"] = 1
    postfix_expr = []
    s = Stack()
    for item in infix_expr.split():
        # 如果标记是操作数，将其附加到输出列表的末尾
        if item not in prec.keys():
            postfix_expr.append(item)
        # 如果标记是左括号，将其压到 s 上
        elif item == '(':
            s.push(item)
        # 如果标记是右括号，则弹出 s，直到删除相应的左括号。将每个运算符附加到
        # 输出列表的末尾
        elif item == ')':
            while s.peek() != '(':
                postfix_expr.append(s.pop())
            s.pop()
        # 如果标记是运算符， *，/，+  或  -  ，将其压入 s。但是，首先删除已经在
        # s 中具有更高或相等优先级的任何运算符，并将它们加到输出列表中
        else:
            while (not s.is_empty()) \
                    and (prec[s.peek()] >= prec[item]):
                postfix_expr.append(s.pop())
            s.push(item)
        print(s.items.show())
    # 当输入表达式被完全处理时，检查 s。仍然在栈上的任何运算符都可以删除并加到
    # 输出列表的末尾
    while not s.is_empty():
        postfix_expr.append(s.pop())

    return ' '.join(postfix_expr)

def postfix_eval(postfix_expr):
    s = Stack()
    for item in postfix_expr.split():
        # 如果不是运算符号，压栈
        if item not in '+-*/':
            s.push(item)
        else:
            # 如果是运算符号，取出栈上最近两个数字进行运算
            # 然后，再将结果压回栈
            op2 = int(s.pop())
            op1 = int(s.pop())
            print(op1, item, op2)
            result = do_match(item, op1, op2)
            s.push(result)
        print(s.items.show())
    return result

# 运行结果
def do_match(op, op1, op2):
    if op == '+':
        return op1 + op2
    elif op == '-':
        return op1 - op2
    elif op == '*':
        return op1 * op2
    elif op == '/':
        return op1 / op2
    else:
        raise Exception('Error operation!')

infix_str = '( 23 + 2 ) * 5 - 280 / ( 4 + 11 * 6 - 35 )'

postfix_output = infix_to_postfix(infix_str)
print(infix_str)
print(postfix_output)
postfix_result = postfix_eval(postfix_output)
print(postfix_result)