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Author: hogan-tech

4054-count-distinct-integers-after-removing-zeros/4054-count-distinct-integers-after-removing-zeros.py

@@ -0,0 +1,34 @@
+# time complexity: O(n)
+# space complexity: O(n)
+class Solution:
+    def countDistinct(self, n: int) -> int:
+        s = str(n)
+        L = len(s)
+
+        total = 0
+        for length in range(1, L):
+            total += 9 ** length
+
+        dp = [[0] * 2 for _ in range(L + 1)]
+
+        dp[L][0] = 1
+        dp[L][1] = 1
+
+        for i in range(L - 1, -1, -1):
+            limit = int(s[i])
+            for tight in (0, 1):
+                maxDigit = limit if tight else 9
+                result = 0
+                for dig in range(1, maxDigit + 1):
+                    newTight = tight and (dig == maxDigit)
+                    result += dp[i + 1][newTight]
+                dp[i][tight] = result
+
+        total += dp[0][1]
+        return total
+
+
+n = 10
+print(Solution().countDistinct(n))
+n = 3
+print(Solution().countDistinct(n))