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Author: hogan-tech

1159-smallest-subsequence-of-distinct-characters/1159-smallest-subsequence-of-distinct-characters.py

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+# time complexity: O(n)
+# space complexity: O(n)
+class Solution:
+    def smallestSubsequence(self, s: str) -> str:
+        stack = []
+        seen = set()
+        lastCharIdx = {c: i for i, c in enumerate(s)}
+
+        for i, c in enumerate(s):
+            if c not in seen:
+                while stack and c < stack[-1] and i < lastCharIdx[stack[-1]]:
+                    seen.discard(stack.pop())
+                seen.add(c)
+                stack.append(c)
+
+        return ''.join(stack)
+
+
+s = "bcabc"
+print(Solution().smallestSubsequence(s))
+s = "cbacdcbc"
+print(Solution().smallestSubsequence(s))