三刷316

Author: diguage

docs/0316-remove-duplicate-letters.adoc

@@ -1,7 +1,7 @@
 [#0316-remove-duplicate-letters]
 = 316. 去除重复字母
 
-https://leetcode.cn/problems/remove-duplicate-letters/[LeetCode - 316. 去除重复字母 ^]
+https://leetcode.cn/problems/remove-duplicate-letters/[LeetCode - 316. 去除重复字母^]
 
 给你一个字符串 `s`，请你去除字符串中重复的字母，使得每个字母只出现一次。需保证 *返回结果的字典序最小*（要求不能打乱其他字符的相对位置）。
 
@@ -50,6 +50,15 @@ include::{sourcedir}/_0316_RemoveDuplicateLetters.java[tag=answer]
 include::{sourcedir}/_0316_RemoveDuplicateLetters_2.java[tag=answer]
 ----
 --
+
+三刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0316_RemoveDuplicateLetters_3.java[tag=answer]
+----
+--
 ====
 
 

logbook/202503.adoc

@@ -1509,6 +1509,11 @@ endif::[]
 |{doc_base_url}/0003-longest-substring-without-repeating-characters.adoc[题解]
 |✅ 复习 {doc_base_url}/0000-09-sliding-window.adoc[Sliding Window 滑动窗口]。我采用的是计数法，也可以采用地址法。
 
+|{counter:codes2503}
+|{leetcode_base_url}/remove-duplicate-letters/[316. 去除重复字母^]
+|{doc_base_url}/0316-remove-duplicate-letters.adoc[题解]
+|❌ 复习 {doc_base_url}/0000-10-monotonic-stack.adoc[Monotonic Stack 单调栈]。知道是单调栈，代码还是没写出来！看到题解，又里面秒懂。
+
 |===
 
 截止目前，本轮练习一共完成 {codes2503} 道题。

src/main/java/com/diguage/algo/leetcode/_0316_RemoveDuplicateLetters_3.java

@@ -0,0 +1,38 @@
+package com.diguage.algo.leetcode;
+
+public class _0316_RemoveDuplicateLetters_3 {
+  // tag::answer[]
+
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2025-09-11 21:13:45
+   */
+  public String removeDuplicateLetters(String s) {
+    char[] chars = s.toCharArray();
+    int[] counter = new int[26];
+    for (char c : chars) {
+      counter[c - 'a']++;
+    }
+    boolean[] added = new boolean[26];
+    StringBuilder result = new StringBuilder();
+    for (char c : chars) {
+      int idx = c - 'a';
+      counter[c - 'a']--;
+      if (added[idx]) {
+        continue;
+      }
+      while (!result.isEmpty() && result.charAt(result.length() - 1) > c) {
+        int lastIdx = result.charAt(result.length() - 1) - 'a';
+        if (counter[lastIdx] == 0) {
+          break;
+        }
+        result.deleteCharAt(result.length() - 1);
+        added[lastIdx] = false;
+      }
+      result.append(c);
+      added[idx] = true;
+    }
+    return result.toString();
+  }
+  // end::answer[]
+}