python中具有3位数字的最高回文 [英] highest palindrome with 3 digit numbers in python

问题描述

问题4来自 http://projecteuler.net/，它说:

回文数在两个方向上都相同.由两个两位数的乘积组成的最大回文率是9009 = 91 * 99.

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 * 99.

找出由两个3位数组成的乘积所产生的最大回文.

Find the largest palindrome made from the product of two 3-digit numbers.

我在这里有此代码

def isPalindrome(num):
    return str(num) == str(num)[::-1]
def largest(bot, top):
    for x in range(top, bot, -1):
        for y in range(top,bot, -1):
            if isPalindrome(x*y):
                return x*y
print largest(100,999)

它应该找到最大的回文，它吐出580085，我认为是正确的，但是欧拉项目并不这么认为，我在这里有问题吗?

It should find the largest palindrome, it spits out 580085 which I believe to be correct, but project euler doesn't think so, do I have something wrong here?

当我崇敬for循环时，我没有想到，我删除了检查最大的东西的方法，这使我很愚蠢.这是工作代码

When I revered the for loop I didn't think it through, I removed the thing that checks for the biggest, silly me. Heres the working code

def isPalindrome(num):
    return str(num) == str(num)[::-1]
def largest(bot, top):
    z = 0
    for x in range(top, bot, -1):
        for y in range(top,bot, -1):
            if isPalindrome(x*y):
                if x*y > z:
                    z = x*y
    return z
print largest(100,999)

它吐出906609

推荐答案

反向迭代找不到最大的x*y，而是找到最大的x回文.答案比580085大.它的x较小，但y较大.

Iterating in reverse doesn't find the largest x*y, it finds the palindrome with the largest x. There's a larger answer than 580085; it has a smaller x but a larger y.

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