Added 641. Design Circular Deque problem (Topic : Queue)

Java/design-circular-deque.java

@@ -0,0 +1,148 @@
+/* We will use an array to store our elements.
+Find the comments for a step by step description of the code. */
+
+
+public class MyCircularDeque {
+
+
+ int size;	//	keeping the count of elements in your array
+ int front = -1;	//	keeping the index of front 
+ int rear = -1;	//	keeping the index of rear
+ int capacity;	//	total capacity of our DS
+ int arr[];	//	array to store the elements
+
+
+ /** Initialize your data structure here. Set the size of the deque to be k. */
+ public MyCircularDeque(int k) {	//	initialising capacity as k
+ this.size = 0 ;	//	and initialising the array
+ this.capacity = k;
+ arr = new int[k];
+ }
+
+ /** Adds an item at the front of Deque. Return true if the operation is successful. */
+ public boolean insertFront(int value) {
+ if( (this.size == this.capacity))	// means queue is full
+ return false;
+
+ if(front == -1) {	// means queue is empty
+ arr[0] = value;
+ front = 0;
+ rear = 0;
+ this.size ++;	//	increase the size and return true
+ return true;
+ }
+
+ if(front == 0) {	// if front is at 0, then add at last and make front as last
+ arr[this.capacity - 1] = value;
+ front = this.capacity - 1;
+ }else{	// else add to the left of front and make front as front - 1;
+ arr[front - 1] = value;
+ front --;
+ }
+ this.size ++;	//	increase the size and return true..
+ return true;
+ }
+
+ /** Adds an item at the rear of Deque. Return true if the operation is successful. */
+ public boolean insertLast(int value) {
+
+ if(this.size == this.capacity)	//	means queue is full
+ return false;
+
+ if(rear == -1) {	//	means queue is empty
+ arr[0] = value;	//	add the first element and return true
+ front = 0;
+ rear = 0;
+ this.size ++;
+ return true;
+ }
+
+ if(rear == this.capacity - 1) {	//	if rear is at last, means we will have to add this element at first
+ arr[0] = value;	//	position and make rear as first
+ rear = 0;
+ }else {
+ arr[rear + 1] = value;	//	if rear is not at last, add to rear + 1 and 
+ rear ++;	//	increment rear
+ }
+ this.size ++;	//	increase the size and return true
+ return true; 
+ }
+
+ /** Deletes an item from the front of Deque. Return true if the operation is successful. */
+ public boolean deleteFront() {
+
+ if(this.size == 0)	//	means queue is empty, cannot delete any element.
+ return false;
+
+ if(this.size == 1) {	//	if there is only one element, then remove it(mark it as 0) and
+ arr[rear] = 0;
+ rear = -1;	//	mark rear and front as -1(like it was initially)...
+ front = -1;
+ this.size --;	//	also decrease the size by 1(to 0)
+ return true;	//	and return true to mark this operation as successful ...
+ }
+
+ if(front == this.capacity -1) {	//	if front is at last position, delete that position 
+ arr[front] = 0;	//	and increment front by 1, so front will now be at 0
+ front = 0;
+ this.size --;	// decrease the size by 1 marking it as empty
+ return true;
+ }
+ arr[front] = 0;	//	if front is not at last, delete from the front and increment front by 1 
+ front ++;
+ this.size --;	//	decrease the size by 1 marking it as empty
+ return true;
+ }
+
+ /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
+ public boolean deleteLast() {
+
+ if(this.size == 0)	//	means queue is empty
+ return false;
+
+ if(this.size == 1) {	//	if there is only one element, then remove it(mark it as 0) and
+ arr[rear] = 0;	//	mark rear and front as -1(like it was initially)...
+ rear = -1;
+ front = -1;
+ this.size --;	//	also decrease the size to 0
+ return true;	//	and return true to mark this operation as successful ...
+ }
+
+ if(rear == 0) {	//	if there are more than one element in the array, 
+ arr[rear] = 0;	//	and rear is at 0, then delete the element and reduce rear by 1
+ rear = this.capacity - 1;	//	so basically rear will fall back to last position...
+ this.size --;
+ }else {
+ arr[rear] = 0;	//	if rear is not at 0, then decrease rear by 1
+ rear --;
+ this.size --;
+ }
+ return true;	//	return true to mark the operation as successful
+ }
+
+ /** Get the front item from the deque. */
+ public int getFront() {
+ if(this.size == 0) {	//	if array is empty, return -1
+ return -1;
+ }
+ return arr[front];	//	else return the element
+ }
+
+ /** Get the last item from the deque. */
+ public int getRear() {
+ if(this.size == 0) {	//	if array is empty, return -1
+ return -1;
+ }
+ return arr[rear];	//	else return the rear
+ }
+
+ /** Checks whether the circular deque is empty or not. */
+ public boolean isEmpty() {
+ return (this.size == 0);
+ }
+
+ /** Checks whether the circular deque is full or not. */
+ public boolean isFull() {
+ return (this.size == this.capacity);
+ }
+}

README.md

@@ -169,6 +169,7 @@ Check out ---> [Sample PR](https://github.com/codedecks-in/LeetCode-Solutions/pu
 | # | Title | Solution | Time | Space | Difficulty | Tag | Note |
 | --- | ------------------------------------------------------------------------------- | --------------------------------------- | ------ | ------ | ---------- | --------------------- | ---- |
 | 933 | [Number of Recent Calls](https://leetcode.com/problems/number-of-recent-calls/) | [C++](./C++/Number-of-Recent-Calls.cpp) | _O(1)_ | _O(1)_ | Easy | Queue, Sliding Window |
+| 641 | [Design Circular Deque](https://leetcode.com/problems/design-circular-deque/) | [Java](./Java/design-circular-deque.java/) | _O(n)_ | _O(n)_ | Medium | Queue, Design |
 
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