算钱

payment.py

# -*- coding: utf8 -*-
from operator import attrgetter

class Member:
    def __init__(self, name, paid=0):
        self.name = name
        self.paid = paid

    def pay(self, num):
        self.paid += num

    def __repr__(self):
        return "<Member> %s paid %.2f" % (self.name, self.paid)

class Payment:
    def __init__(self, payer, receiver, amount):
        self.payer = payer
        self.receiver = receiver
        self.amount = amount

    def __repr__(self):
        return "<Payment> %s should pay %.2f to %s" % (self.payer.name, self.amount, self.receiver.name)

def calc(members):
    avg_paid = sum([e.paid for e in members])/len(members) # 平均支出
    paid_more, paid_less = [],[]
    payments = []
    # 按支出大于小于平均, 分成两部分
    for member in members:
        temp = member
        if member.paid < avg_paid:
            paid_less.append(temp)
        if member.paid > avg_paid:
            paid_more.append(temp)
    # 多支出的按从多到少排序, 少支出的从少到多排序.
    paid_more.sort(key=attrgetter("paid"), reverse=True)
    paid_less.sort(key=attrgetter("paid"))
    print(paid_more)
    print(paid_less)
    for m_more in paid_more:
        to_get = m_more.paid - avg_paid
        # 少支出者依次向多支出者补钱.
        current_paid_finished = False # 当前这个少支出者是否已经完成补钱. 如果是, 移出
        for m_less in paid_less:
            if to_get == 0: # 当前多支出者的钱已经补完
                break
            to_pay = avg_paid - m_less.paid
            if to_get > to_pay: # 少支出者已补完自己那份, 轮那下一个人继续补钱. 而当前多支出者的钱还没补全, 需要下个人继续补给他
                to_get -= to_pay
                payment = Payment(m_less, m_more, to_pay)
                payments.append(payment)
                continue
            if to_get == to_pay:
                payment = Payment(m_less, m_more, to_pay)
                payments.append(payment)
                current_paid_finished = True
                break
            if to_get < to_pay: # 当前多支出者已经补完, 但少支出者还需要再补一部分, 补给下一个人
                to_pay -= to_get
                payment = Payment(m_less, m_more, to_get)
                payments.append(payment)
                break
        if current_paid_finished:
            paid_less = paid_less[1:]
    for pay in payments:
        print(pay)

if __name__ == "__main__":
    mem1 = Member(name="Gary", paid=150)
    mem2 = Member(name="Li", paid=90)
    mem3 = Member(name="Hu")
    members = [mem1, mem2, mem3]
    calc(members)