count number of palindromic substring

Author: Alagappan Maruthappan

count_palindrome_substring.py

@@ -0,0 +1,29 @@
+# https://leetcode.com/problems/palindromic-substrings/description/
+
+
+class Solution:
+    def countSubstrings(self, s):
+        """
+        :type s: str
+        :rtype: int
+        """
+        ans = 0
+        N = len(s)
+        DP = [[False] * N for i in range(N)]
+        for i in range(N):
+            DP[i][i] = True
+            ans += 1
+        for i in range(N-1):
+            if s[i] == s[i+1]:
+                DP[i][i+1] = True
+                ans += 1
+        for size in range(3, N + 1):
+            for start in range(N-size+1):
+                end = start + size - 1
+                if s[start] == s[end] and DP[start+1][end-1]:
+                    DP[start][end] = True
+                    ans += 1
+        return ans
+
+
+assert Solution().countSubstrings("aaa") == 6