update readme

Author: hogan-tech

.github/test.txt

@@ -1 +1,2 @@
-0941-valid-mountain-array python easy
+0316-remove-duplicate-letters python medium
+1081-smallest-subsequence-of-distinct-characters python medium

0316-remove-duplicate-letters/0316-remove-duplicate-letters.py

@@ -1,15 +1,22 @@
-from collections import Counter
-
-
+# time complexity: O(n)
+# space complexity: O(n)
 class Solution:
     def removeDuplicateLetters(self, s: str) -> str:
-        c = Counter(s)
-        position = 0
-        for i in range(len(s)):
-            if s[i] < s[position]:
-                position = i
-            c[s[i]] -= 1
-            if c[s[i]] == 0:
-                break
-
-        return s[position] + self.removeDuplicateLetters(s[position:].replace(s[position], "")) if s else ""
+        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().removeDuplicateLetters(s))
+s = "cbacdcbc"
+print(Solution().removeDuplicateLetters(s))

0316-remove-duplicate-letters/README.md

@@ -39,6 +39,7 @@
 | 1074 | [Number of Submatrices That Sum to Target](https://leetcode.com/problems/number-of-submatrices-that-sum-to-target/)                                                                          | [Python](./Python/1074-number-of-submatrices-that-sum-to-target.py)                                      | [Hard](./Readme/1074-number-of-submatrices-that-sum-to-target.md)                                        |
 | 1075 | [Project Employees I](https://leetcode.com/problems/project-employees-i/)                                                                                                                    | [SQL](./SQL/1075-project-employees-i.sql)                                                                | [Easy](./Readme/1075-project-employees-i.md)                                                             |
 | 1079 | [Letter Tile Possibilities](https://leetcode.com/problems/letter-tile-possibilities)                                                                                                         | [Python](./Python/1079-letter-tile-possibilities.py)                                                     | [Medium](./Readme/1079-letter-tile-possibilities.md)                                                     |
+| 1081 | [Smallest Subsequence of Distinct Characters](https://leetcode.com/problems/smallest-subsequence-of-distinct-characters)                                                                     | [Python](./Python/1081-smallest-subsequence-of-distinct-characters.py)                                   | [Medium](./Readme/1081-smallest-subsequence-of-distinct-characters.md)                                   |
 | 1086 | [High Five](https://leetcode.com/problems/high-five)                                                                                                                                         | [Python](./Python/1086-high-five.py)                                                                     | [Easy](./Readme/1086-high-five.md)                                                                       |
 | 1087 | [Brace Expansion](https://leetcode.com/problems/brace-expansion)                                                                                                                             | [Python](./Python/1087-brace-expansion.py)                                                               | [Medium](./Readme/1087-brace-expansion.md)                                                               |
 | 1090 | [Largest Values From Labels](https://leetcode.com/problems/largest-values-from-labels)                                                                                                       | [Python](./Python/1090-largest-values-from-labels.py)                                                    | [Medium](./Readme/1090-largest-values-from-labels.md)                                                    |

Python/0316-remove-duplicate-letters.py

@@ -115,27 +115,3 @@ It helps others discover the repo and keeps the project growing.
 ---
 
 Feedback / Questions → open an Issue or reach out on [LinkedIn](https://www.linkedin.com/in/hogan-l/)  
-
-<!---LeetCode Topics Start-->
-# LeetCode Topics
-## String
-|  |
-| ------- |
-| [0316-remove-duplicate-letters](https://github.com/hogan-tech/leetcode-solution/tree/master/0316-remove-duplicate-letters) |
-| [1159-smallest-subsequence-of-distinct-characters](https://github.com/hogan-tech/leetcode-solution/tree/master/1159-smallest-subsequence-of-distinct-characters) |
-## Stack
-|  |
-| ------- |
-| [0316-remove-duplicate-letters](https://github.com/hogan-tech/leetcode-solution/tree/master/0316-remove-duplicate-letters) |
-| [1159-smallest-subsequence-of-distinct-characters](https://github.com/hogan-tech/leetcode-solution/tree/master/1159-smallest-subsequence-of-distinct-characters) |
-## Greedy
-|  |
-| ------- |
-| [0316-remove-duplicate-letters](https://github.com/hogan-tech/leetcode-solution/tree/master/0316-remove-duplicate-letters) |
-| [1159-smallest-subsequence-of-distinct-characters](https://github.com/hogan-tech/leetcode-solution/tree/master/1159-smallest-subsequence-of-distinct-characters) |
-## Monotonic Stack
-|  |
-| ------- |
-| [0316-remove-duplicate-letters](https://github.com/hogan-tech/leetcode-solution/tree/master/0316-remove-duplicate-letters) |
-| [1159-smallest-subsequence-of-distinct-characters](https://github.com/hogan-tech/leetcode-solution/tree/master/1159-smallest-subsequence-of-distinct-characters) |
-<!---LeetCode Topics End-->

1159-smallest-subsequence-of-distinct-characters/1159-smallest-subsequence-of-distinct-characters.py renamed to Python/1081-smallest-subsequence-of-distinct-characters.py

@@ -1,16 +1,18 @@
-<h2><a href="https://leetcode.com/problems/remove-duplicate-letters/">316. Remove Duplicate Letters</a></h2><h3>Medium</h3><hr><div><p>Given a string <code>s</code>, remove duplicate letters so that every letter appears once and only once. You must make sure your result is <span data-keyword="lexicographically-smaller-string"><strong>the smallest in lexicographical order</strong></span> among all possible results.</p>
+<h2><a href="https://leetcode.com/problems/remove-duplicate-letters">316. Remove Duplicate Letters</a></h2><h3>Medium</h3><hr><p>Given a string <code>s</code>, remove duplicate letters so that every letter appears once and only once. You must make sure your result is <span data-keyword="lexicographically-smaller-string"><strong>the smallest in lexicographical order</strong></span> among all possible results.</p>
 
 <p>&nbsp;</p>
 <p><strong class="example">Example 1:</strong></p>
 
-<pre><strong>Input:</strong> s = "bcabc"
-<strong>Output:</strong> "abc"
+<pre>
+<strong>Input:</strong> s = &quot;bcabc&quot;
+<strong>Output:</strong> &quot;abc&quot;
 </pre>
 
 <p><strong class="example">Example 2:</strong></p>
 
-<pre><strong>Input:</strong> s = "cbacdcbc"
-<strong>Output:</strong> "acdb"
+<pre>
+<strong>Input:</strong> s = &quot;cbacdcbc&quot;
+<strong>Output:</strong> &quot;acdb&quot;
 </pre>
 
 <p>&nbsp;</p>
@@ -23,4 +25,3 @@
 
 <p>&nbsp;</p>
 <p><strong>Note:</strong> This question is the same as 1081: <a href="https://leetcode.com/problems/smallest-subsequence-of-distinct-characters/" target="_blank">https://leetcode.com/problems/smallest-subsequence-of-distinct-characters/</a></p>
-</div>