数据结构 顺序表实现队列 回顾练习

顺序表队列 入队0（n） 出队0（1）

列表的下端为出口

这里需要注意的是 self._elems = [None] * init_len

不然后面的程序会出现 IndexError 

#!/usr/bin/env python3

class QueueUnderflow(ValueError):
        pass

class Simple_SQueue(object):
        def __init__(self, init_len=8):
                self.len = init_len
                self._elems = [None] * init_len
                self.num = 0

        def is_empty(self):
                return self._elems == []

        def count(self):
                return self.num

        def is_full(self):
                return self.num == self.len

        def dequeue(self):
                if self.num == 0:
                        raise QueueUnderflow
                e = self._elems[self.num-1]
                self.num -= 1
                return e

        def peek(self):
                if self.num == 0:
                        raise QueueUnderflow
                e = self._elems[self.num-1]
                return e

        def enqueue(self, elem):
                if self.is_full():
                        self._extends(init_len)
                if self.num == 0:
                        self._elems[0] = elem
                        self.num += 1
                        return
                for i in range(self.num,0,-1):
                        self._elems[i] = self._elems[i-1]
                self._elems[0] = elem
                self.num += 1

        def _extends(self):
                pass

        def bianli(self):
                li = []
                for i in range(self.num-1,-1,-1):
                        li.append(self._elems[i])
                return li

if __name__ == '__main__':
        sq = Simple_SQueue()
        for i in [1,2,3,4,5]:
            sq.enqueue(i)
        print(sq.bianli())
        sq.dequeue()
        sq.dequeue()
        print(sq.bianli())