Added digit_dp problem with python solution

Author: Agrim2411

digit_dp.py

@@ -0,0 +1,21 @@
+# Problem Link -: https://leetcode.com/problems/numbers-at-most-n-given-digit-set/
+# Problem -: Numbers At Most N Given Digit Set
+# Given an array of digits which is sorted in non-decreasing order. You can write numbers using each digits[i] as many times as we want. For example, if digits = ['1','3','5'], we may write numbers such as '13', '551', and '1351315'.
+# Return the number of positive integers that can be generated that are less than or equal to a given integer n.
+
+
+
+# Python Digit DP Solution
+def atMostNGivenDigitSet(self, D: List[str], N: int) -> int:
+        D = list(map(int, D))
+        N = list(map(int, str(N)))
+
+        @functools.lru_cache(None)
+        def dp(i, isPrefix, isBigger):
+            if i == len(N):
+                return not isBigger
+            if not isPrefix and not isBigger:
+                return 1 + len(D) * dp(i + 1, False, False)
+            return 1 + sum(dp(i + 1, isPrefix and d == N[i], isBigger or (isPrefix and d > N[i])) for d in D)
+
+        return dp(0, True, False) - 1