Add solution for Palindromic Substrings

dp/leetcode/palindromic-substrings.py

@@ -0,0 +1,23 @@
+class Solution:
+    def countSubstrings(self, s: str) -> int:
+        n=len(s)
+        count=0
+        def checker(left,right):
+            nonlocal count
+            while left>=0 and right<n:
+                if s[left]==s[right]:
+                    count+=1
+                    left-=1
+                    right+=1
+                else:
+                    break
+        for i in range(n):
+            checker(i,i)
+            checker(i,i+1)
+        return count
+
+
+
+
+
+