a5

README.md

@@ -10,6 +10,8 @@ leetcode 题解
 
 [4. Median of Two Sorted Arrays](Solution/1-50/4.md)
 
+[5. Longest Palindromic Substring](Solution/1-50/5.md)
+
 [7. Reverse Integer](Solution/1-50/7.md)
 
 [8. String to Integer (atoi)](Solution/1-50/8.md)

Solution/1-50/5.md

@@ -0,0 +1,34 @@
+#5. Longest Palindromic Substring
+[题目链接](https://leetcode.com/problems/longest-palindromic-substring/#/description)
+```python
+class Solution(object):
+    start = maxLength = 0
+    def findPalindrome(self, s, i, j):
+        """
+        :param s: str
+        :param i: int
+        :param j: int
+        :return: 
+        """
+        while i >= 0 and j < len(s) and s[i] == s[j]:
+            i -= 1
+            j += 1
+        length = j - i - 1
+        if length > self.maxLength:
+            self.maxLength = length
+            self.start = i + 1
+
+    def longestPalindrome(self, s):
+        """
+        :type s: str
+        :rtype: str
+        """
+        if len(s) <= 2:
+            return s
+        # 遍历字符串计算，分奇数情况和偶数情况
+        for i in range(len(s)):
+            self.findPalindrome(s, i, i)
+            self.findPalindrome(s, i, i + 1)
+        return s[self.start: self.start + self.maxLength]
+
+```