leecode的第五题完成，

Author: ssjssh

src/ssj/leecode/longest_palindromic_substring.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python
+# -*- coding:UTF-8
+__author__ = 'shenshijun'
+"""
+Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.
+
+我的解法就是这个解法：http://taop.marchtea.com/01.05.html
+感谢
+"""
+
+
+class Solution(object):
+    def longestPalindrome(self, original):
+        """
+        :type s: str
+        :rtype: str
+        """
+        if not original:
+            return 0
+        s = self.__preProcess(original)
+        longest_right_bound = 0
+        longest_median = 0
+        pali_list = [1 for i in range(len(s))]
+        # 注意迭代位置，为了不出现越界，最前和最后的字符串是不会被遍历的
+        for i in range(1, len(s) - 1):
+            # 这边使用的是对称的原理，使得可以快速个p[i]一个基础的值
+            if longest_right_bound > i:
+                if longest_right_bound - i <= pali_list[2 * longest_median - i]:
+                    pali_list[i] = longest_right_bound - i
+                else:
+                    pali_list[i] = pali_list[2 * longest_median - i]
+            # 在字符串的最前面和最后面都必须加上一个特殊字符，用于防止越界
+            # 另一个方法是在每次循环的时候都判断边界，但是效率比直接加特殊字符低
+            while s[i + pali_list[i]] == s[i - pali_list[i]]:
+                pali_list[i] += 1
+            if pali_list[i] >= longest_right_bound - longest_median:
+                longest_right_bound = pali_list[i] + i
+                longest_median = i
+        return self.__clearString(s[2 * longest_median - longest_right_bound + 1:longest_right_bound])
+
+    def __clearString(self, sub_str):
+        return "".join([ch for ch in sub_str if ch != '#'])
+
+    def __preProcess(self, s):
+        str_list = ['#{}'.format(ele) for ele in s]
+        str_list.append("#$")
+        str_list.insert(0, '^')
+        return "".join(str_list)
+
+
+def main():
+    print(Solution().longestPalindrome("bbbbbb"))  # 6
+    print(Solution().longestPalindrome("fqwefqwefqwadccdaafwfawef"))  # 6
+    print(Solution().longestPalindrome("qwefqwefqsjsjsssgsssjsjsg3q4gekwSKDFKALJKFIUWIUEFWEG"))  # 15
+    print(Solution().longestPalindrome("ababababa"))  # 10
+
+
+if __name__ == "__main__":
+    main()