add q316

yuanguangxin · yuanguangxin · commit e7dd9f3eb688 · 2020-03-06T20:30:19.000+08:00
diff --git a/.idea/workspace.xml b/.idea/workspace.xml
diff --git a/README.md b/README.md
@@ -56,6 +56,7 @@
 
 * [q20_有效的括号](/src/栈相关/q20_有效的括号)
 * [q224_基本计算器](/src/栈相关/q224_基本计算器)
+* [q316_去除重复字母](/src/栈相关/q316_去除重复字母)
 
 ### 堆相关
 
diff --git a/src/栈相关/q316_去除重复字母/Solution.java b/src/栈相关/q316_去除重复字母/Solution.java
@@ -0,0 +1,28 @@
+package 栈相关.q316_去除重复字母;
+
+import java.util.Stack;
+
+/**
+ * 栈操作 o(n*log(n))
+ */
+public class Solution {
+
+    public String removeDuplicateLetters(String s) {
+        Stack<Character> stack = new Stack<>();
+        for (int i = 0; i < s.length(); i++) {
+            Character c = s.charAt(i);
+            if (stack.contains(c)) {
+                continue;
+            }
+            while (!stack.isEmpty() && stack.peek() > c && s.indexOf(stack.peek(), i) != -1) {
+                stack.pop();
+            }
+            stack.push(c);
+        }
+        String rs = "";
+        for (int i = 0; i < stack.size(); i++) {
+            rs += stack.get(i);
+        }
+        return rs;
+    }
+}
