判断一段序列是否为回文palindrome

参考：

 

输入一段序列，判断该序列是否为回文

1，分别从左到右、从右到左判断字符是否相等。

 

 

def is_palindrome(text):

    p1 = 0
    p2 = len(text) - 1
    t = text.lower()
    while p1 < p2:

        if not text[p1].isalnum():
            p1 += 1

        elif not text[p2].isalnum():
            p2 -= 1

        else:
            print t[p1],t[p2]
            if t[p1] != t[p2]:
                return False
        p1 += 1
        p2 -= 1

    return True

if is_palindrome(raw_input("Input sentence: ")):
    print "Palindrome!"

 

2，直接将整个序列反转，判断源序列和反转后的序列是否相等

 

s = raw_input("Sentence? ").replace(" ", "").lower()

if s == s[::-1]:
    print "Your sentence is a palindrome"
else:
    print "Not a palindrome"