LeetCode 刷题记录: 5. Longest Palindromic Substring [Python]

class Solution:
    """
    @param s: input string
    @return: the longest palindromic substring
    """
    def longestPalindrome(self, s):
        # write your code here
        if not s:
            return s
        T = '#'
        for c in s:
            T += c
            T += '#'
        radius = [0]*len(T)

        c, r = 0, -1
        maxr, maxs = -1, ''
        for i in range(len(T)):
            if r > i:
                j = c-i-c
                radius[i] = min(radius[j], c+r-1)

            while -1 < i-radius[i] and i+radius[i] < len(T):
                if T[i-radius[i]] == T[i+radius[i]]:
                    radius[i] += 1
                else:
                    break

            if radius[i] >= r:
                c, r = i, radius[i]-1
            if r > maxr:
                maxr = r
                maxs = s[(i-r)//2 : (i+r)//2]

        return maxs