Problem 4: Largest palindrome product

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

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

3位数的话，就从999开始，为了减少遍历次数，就先从999-900，如果没有条件满足，再放大这个范围

l = []
for i in range(999, 900, -1):
    for j in range(999, 900, -1):
            n = str(i * j)
            if n == n[::-1]:
                l.append(int(n))
print(max(l))

执行结果：906609