约瑟夫问题

class Child(object):
    first = None
    def __init__(self, no=None, pNext = None):
        self.no = no
        self.pNext = pNext

    def __str__(self):
        return self.no

    def add(self, n = 1000):
        cur = None
        for i in range(n):
            child = Child(i+1)
            if i==0:
                self.first = child
                self.first.pNext = child
                cur = self.first
            else:
                cur.pNext = child
                child.pNext = self.first
                cur = cur.pNext

    def show(self):
        cur = self.first
        while cur.pNext != self.first:
            print('小孩的编号是%s' % cur.no)
            cur = cur.pNext
        print('小孩的编号是%s' % cur.no)

    # k = 2 m = 3000
    def countChild(self, m, k):
        tail = self.first

        while tail.pNext != self.first:
            tail = tail.pNext

        # 当退出循环的时候, 已经在first的后面

        for i in range(k - 1):
            self.first = self.first.pNext
            tail = tail.pNext

        # 数两下, tail 和 first走一次
        # 数三下, tail 和 first走两次
        while self.first.pNext != self.first:
            for i in range(m - 1):
                tail = tail.pNext
                self.first = self.first.pNext

            self.first = self.first.pNext
            tail.pNext = self.first

        print('留在圈中的小孩是%s' % tail.no)


c = Child()
c.add()
c.show()
c.countChild(3, 2)