One Edit Distance

CC189里面的做法，双指针比对就行了，主要是要能写的简洁

class Solution(object):
    def isOneEditDistance(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: bool
        """
        n, m = len(s), len(t)
        if abs(n - m) > 1:
            return False

        for i in xrange(min(n, m)):
            if s[i] != t[i]:
                if n == m:
                    return s[i + 1:] == t[i + 1:]
                elif n > m:
                    return s[i + 1:] == t[i:]
                else:
                    return s[i:] == t[i + 1:]

        return n != m