add a solution for 1209

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/secondthousand/_1209.java

@@ -115,4 +115,42 @@ public String removeDuplicates(String s, int k) {
             return sb.reverse().toString();
         }
     }
+
+    public static class Solution4 {
+        //my completely original solution on 6/19/2024
+        public String removeDuplicates(String s, int k) {
+            Deque<Pair> stack = new LinkedList<>();
+            for (char c : s.toCharArray()) {
+                if (!stack.isEmpty() && stack.peekLast().c == c) {
+                    Pair pair = stack.pollLast();
+                    pair.count = pair.count + 1;
+                    if (pair.count < k) {
+                        stack.addLast(pair);
+                    }
+                } else {
+                    stack.addLast(new Pair(c, 1));
+                }
+            }
+            StringBuilder sb = new StringBuilder();
+            while (!stack.isEmpty()) {
+                Pair pair = stack.pollLast();
+                int count = pair.count;
+                while (count-- > 0) {
+                    sb.append(pair.c);
+                }
+            }
+            return sb.reverse().toString();
+        }
+
+        class Pair {
+            char c;
+            int count;
+
+            public Pair(char c, int count) {
+                this.c = c;
+                this.count = count;
+            }
+        }
+
+    }
 }

src/test/java/com/fishercoder/secondthousand/_1209Test.java

@@ -1,29 +1,32 @@
 package com.fishercoder.secondthousand;
 
 import com.fishercoder.solutions.secondthousand._1209;
-import org.junit.BeforeClass;
-import org.junit.Test;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
 
-import static org.junit.Assert.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 public class _1209Test {
 
     private static _1209.Solution1 solution1;
     private static _1209.Solution2 solution2;
     private static _1209.Solution3 solution3;
+    private static _1209.Solution4 solution4;
 
-    @BeforeClass
-    public static void setup() {
+    @BeforeEach
+    public void setup() {
         solution1 = new _1209.Solution1();
         solution2 = new _1209.Solution2();
         solution3 = new _1209.Solution3();
+        solution4 = new _1209.Solution4();
     }
 
     @Test
     public void test1() {
         assertEquals("abcd", solution1.removeDuplicates("abcd", 2));
         assertEquals("abcd", solution2.removeDuplicates("abcd", 2));
         assertEquals("abcd", solution3.removeDuplicates("abcd", 2));
+        assertEquals("abcd", solution4.removeDuplicates("abcd", 2));
     }
 
     @Test