Python数生命数

Question

为了说明这一点，我们有两种动物，一种是猪，另一种是鸡。用户输入这两种动物的头和腿的数量。例如，如果我们运行这个程序，输入20头56条腿，我们得到12只鸡和8头猪。看看这里：

def solve(numLegs, numHeads):
    for numChicks in range(0, numHeads + 1): # how we get 12 chickens here?
        numPigs = numHeads - numChicks # numpigs = 20 - 12 = 8 ?
        totLegs = 4 * numPigs + 2* numChicks # 4 * 8 + 2 * 12 ?
        if totLegs == numLegs:
           return [numPigs, numChicks]
    return[None, None]

def barnYard():
    heads = int(raw_input('Enter number of heads:'))
    legs = int(raw_input('Enter number of legs:'))
    pigs, chickens = solve(legs, heads)
    if pigs = None:
       print 'there is no solution'
    else:
        print 'number of pigs:' , pigs
        pirnt 'number of chickes:', chickens

我们计算totLegs = 4 * numPigs + 2* numChicks知道猪有4条腿，鸡有2条腿，然后验证这是否与输入的腿数匹配，对吗？但是现在的问题是for numChicks in range(0, numHeads + 1):它如何找到鸡肉的数量是12？如果没有找到鸡的数量，如果我没有错的话，我们就不能继续下一行了。你能解释一下吗？这让我很困惑。代数版本可以在这里找到。link

Answer 1

Don't make your life more complicated than it already is，只需使用print command to see the intermediate values，它是simple algebra。顺便说一句，您的代码中有many errors，它doesn't even compile（主要是typos，比如{}，而不是{}）。请看这里fixed code which works:

def solve(numLegs, numHeads):
    for numChicks in range(0, numHeads + 1): #we have got 12 chickens here?
        print "numChicks = ", numChicks
        numPigs = numHeads - numChicks
        print "numPigs = ", numPigs
        totLegs = 4 * numPigs + 2* numChicks
        print "totLegs = ",totLegs
        if totLegs == numLegs:
            print "numLegs = ",numLegs
            print "numPigs = ",numPigs
            print "numChicks = ",numChicks
            return [numPigs, numChicks]
    return[None, None]

def barnYard():
    heads = int(raw_input('Enter number of heads:'))
    legs = int(raw_input('Enter number of legs:'))
    pigs, chickens = solve(legs, heads)
    if pigs == None:
       print 'there is no solution'
    else:
        print 'number of pigs:' , pigs
        print 'number of chicken:', chickens



if __name__ == "__main__":
    barnYard()

输出

^{pr2}$

这是简单的数学。You have 20 heads, 56 legs. every pigs has 4 legs, every chicken 2 legs

所以

56 = 4*X+2*Y
   X+Y=20

也就是说X = 20 - Y

然后56 = 4*(20-Y)+2*Y => 56 = 80 -4Y+2Y => 2Y = 80 - 56 => 2Y = 24 => Y = 12 Chicken

然后X + 12 = 20 => X = 8 Pigs

：天

希望有帮助！！在