Create Design Front Middle Back Queue.java

varunu28 · web-flow · commit 5a23685ddb4b · 2021-11-19T09:07:12.000-08:00
diff --git a/Medium/Design Front Middle Back Queue.java b/Medium/Design Front Middle Back Queue.java
@@ -0,0 +1,64 @@
+class FrontMiddleBackQueue {
+
+  Deque<Integer> frontQueue;
+  Deque<Integer> backQueue;
+
+  public FrontMiddleBackQueue() {
+    frontQueue = new ArrayDeque<>();
+    backQueue = new ArrayDeque<>();
+  }
+
+  public void pushFront(int val) {
+    frontQueue.addFirst(val);
+  }
+
+  public void pushMiddle(int val) {
+    while (frontQueue.size() + 1 < backQueue.size()) {
+      frontQueue.addLast(backQueue.removeFirst());
+    }
+    while (frontQueue.size() > backQueue.size()) {
+      backQueue.addFirst(frontQueue.removeLast());
+    }
+    frontQueue.addLast(val);
+  }
+
+  public void pushBack(int val) {
+    backQueue.addLast(val);
+  }
+
+  public int popFront() {
+    return frontQueue.isEmpty()
+        ? (backQueue.isEmpty() ? -1 : backQueue.removeFirst())
+        : frontQueue.removeFirst();
+  }
+
+  public int popMiddle() {
+    if (frontQueue.isEmpty() && backQueue.isEmpty()) {
+      return -1;
+    }
+    while (frontQueue.size() < backQueue.size()) {
+      frontQueue.addLast(backQueue.removeFirst());
+    }
+    while (frontQueue.size() > backQueue.size() + 1) {
+      backQueue.addFirst(frontQueue.removeLast());
+    }
+    return !frontQueue.isEmpty() ? frontQueue.removeLast() : backQueue.removeFirst();
+  }
+
+  public int popBack() {
+    return backQueue.isEmpty()
+        ? (frontQueue.isEmpty() ? -1 : frontQueue.removeLast())
+        : backQueue.removeLast();
+  }
+}
+
+/**
+ * Your FrontMiddleBackQueue object will be instantiated and called as such:
+ * FrontMiddleBackQueue obj = new FrontMiddleBackQueue();
+ * obj.pushFront(val);
+ * obj.pushMiddle(val);
+ * obj.pushBack(val);
+ * int param_4 = obj.popFront();
+ * int param_5 = obj.popMiddle();
+ * int param_6 = obj.popBack();
+ */
