add 1209

fishercoder1534 · fishercoder1534 · commit e51b36e256f4 · 2020-02-13T07:36:14.000-08:00
diff --git a/README.md b/README.md
@@ -61,6 +61,7 @@ _If you like this project, please leave me a star._ &#9733;
 |1217|[Play with Chips](https://leetcode.com/problems/play-with-chips/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1217.java) |   |Easy|Array, Math, Greedy|
 |1214|[Two Sum BSTs](https://leetcode.com/problems/two-sum-bsts/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1214.java) |   |Medium| Binary Search Tree|
 |1213|[Intersection of Three Sorted Arrays](https://leetcode.com/problems/intersection-of-three-sorted-arrays/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1213.java) |   [:tv:](https://www.youtube.com/watch?v=zceoOrHSHNQ)|Easy||
+|1209|[Remove All Adjacent Duplicates in String II](https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1207.java) ||Medium|Stack|
 |1207|[Unique Number of Occurrences](https://leetcode.com/problems/unique-number-of-occurrences/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1207.java) | [:tv:](https://www.youtube.com/watch?v=_NYimlZY1PE)|Easy||
 |1200|[Minimum Absolute Difference](https://leetcode.com/problems/minimum-absolute-difference/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1200.java) | [:tv:](https://www.youtube.com/watch?v=mH1aEjOEjcQ)|Easy||
 |1198|[Find Smallest Common Element in All Rows](https://leetcode.com/problems/find-smallest-common-element-in-all-rows/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1198.java) | [:tv:](https://www.youtube.com/watch?v=RMiofZrTmWo)|Easy||
diff --git a/src/main/java/com/fishercoder/solutions/_1209.java b/src/main/java/com/fishercoder/solutions/_1209.java
@@ -0,0 +1,77 @@
+package com.fishercoder.solutions;
+
+import java.util.Stack;
+
+/**
+ * 1209. Remove All Adjacent Duplicates in String II
+ *
+ * Given a string s, a k duplicate removal consists of choosing k adjacent and equal
+ * letters from s and removing them causing the left and the right side of the deleted substring to concatenate together.
+ * We repeatedly make k duplicate removals on s until we no longer can.
+ * Return the final string after all such duplicate removals have been made.
+ * It is guaranteed that the answer is unique.
+ *
+ * Example 1:
+ * Input: s = "abcd", k = 2
+ * Output: "abcd"
+ * Explanation: There's nothing to delete.
+ *
+ * Example 2:
+ * Input: s = "deeedbbcccbdaa", k = 3
+ * Output: "aa"
+ * Explanation:
+ * First delete "eee" and "ccc", get "ddbbbdaa"
+ * Then delete "bbb", get "dddaa"
+ * Finally delete "ddd", get "aa"
+ *
+ * Example 3:
+ * Input: s = "pbbcggttciiippooaais", k = 2
+ * Output: "ps"
+ *
+ * Constraints:
+ * 1 <= s.length <= 10^5
+ * 2 <= k <= 10^4
+ * s only contains lower case English letters.
+ * */
+public class _1209 {
+    public static class Solution1 {
+        public String removeDuplicates(String s, int k) {
+            Stack<Character> stack = new Stack<>();
+            char c = s.charAt(0);
+            stack.push(c);
+            int count = 1;
+            for (int i = 1; i < s.length(); i++) {
+                if (s.charAt(i) == c) {
+                    count++;
+                    stack.push(s.charAt(i));
+                    if (count == k) {
+                        while (!stack.isEmpty() && stack.peek() == c) {
+                            stack.pop();
+                        }
+                        count = 0;
+                        if (!stack.isEmpty()) {
+                            c = stack.peek();
+                            while (!stack.isEmpty() && c == stack.peek()) {
+                                count++;
+                                stack.pop();
+                            }
+                            int tmp = count;
+                            while (tmp-- > 0) {
+                                stack.push(c);
+                            }
+                        }
+                    }
+                } else {
+                    c = s.charAt(i);
+                    stack.push(s.charAt(i));
+                    count = 1;
+                }
+            }
+            StringBuilder sb = new StringBuilder();
+            while (!stack.isEmpty()) {
+                sb.append(stack.pop());
+            }
+            return sb.reverse().toString();
+        }
+    }
+}
diff --git a/src/test/java/com/fishercoder/_1209Test.java b/src/test/java/com/fishercoder/_1209Test.java
@@ -0,0 +1,33 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._1209;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _1209Test {
+
+    private static _1209.Solution1 solution1;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _1209.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals("abcd", solution1.removeDuplicates("abcd", 2));
+    }
+
+    @Test
+    public void test2() {
+        assertEquals("aa", solution1.removeDuplicates("deeedbbcccbdaa", 3));
+    }
+
+    @Test
+    public void test3() {
+        assertEquals("ps", solution1.removeDuplicates("pbbcggttciiippooaais", 2));
+    }
+
+}
