Added priority queues

MaxPriorityQueue.java

@@ -0,0 +1,77 @@
+package priorityQueues;
+import java.util.*;
+
+public class MaxPriorityQueue {
+
+	ArrayList<Integer> heap;
+    MaxPriorityQueue(){
+        heap=new ArrayList<>();
+    }
+
+    int getSize(){
+        return heap.size();
+    }
+
+    boolean isEmpty(){
+        return (heap.size()==0);
+    }
+
+    int getMax(){
+        if(isEmpty()){
+            return Integer.MIN_VALUE;
+        }
+        return heap.get(0);
+    }
+
+    void insert(int element){
+		heap.add(element);
+		int childIndex = heap.size() - 1;
+		int parentIndex = (childIndex - 1) / 2;
+
+		while(childIndex > 0){
+			if(heap.get(childIndex) > heap.get(parentIndex)){
+				int temp = heap.get(childIndex);
+				heap.set(childIndex, heap.get(parentIndex));
+				heap.set(parentIndex, temp);
+				childIndex = parentIndex;
+				parentIndex = (childIndex - 1) / 2;
+			}else{
+				return;
+			}
+		}
+	}
+
+    int removeMax(){
+        int maxValue=heap.get(0);
+        int lastIndex=heap.size()-1;
+        heap.set(0,heap.get(lastIndex));
+        heap.remove(heap.size()-1);
+
+        //down-Heapify
+        int index=0;
+        int maxIndex=index;
+        int leftchildIndex=1;
+        int rightchildIndex=2;
+        while(leftchildIndex<heap.size()){
+
+            if(heap.get(leftchildIndex)>heap.get(maxIndex)){
+                maxIndex=leftchildIndex;
+            }
+            if(rightchildIndex<heap.size() && heap.get(rightchildIndex)>heap.get(maxIndex)){
+                maxIndex=rightchildIndex;  
+            }
+            if(maxIndex==index){
+                break;
+            }
+            int temp=heap.get(index);
+            heap.set(index,heap.get(maxIndex));
+            heap.set(maxIndex,temp);
+            index=maxIndex;
+            leftchildIndex=2*index+1;
+            rightchildIndex=2*index+2;
+
+        }
+
+        return maxValue;
+    }
+}

MinPriorityQueue.java

@@ -0,0 +1,81 @@
+package priorityQueues;
+import java.util.*;
+
+public class MinPriorityQueue {
+
+	private ArrayList<Integer> heap;
+
+	public MinPriorityQueue() {
+		heap = new ArrayList<Integer>();
+	}
+
+	boolean isEmpty(){
+		return heap.size() == 0;
+	}
+
+	int size(){
+		return heap.size();
+	}
+
+	int getMin() throws PriorityQueueException{
+		if(isEmpty()){
+			// Throw an exception
+			throw new PriorityQueueException();
+		}
+		return heap.get(0);
+	}
+
+	void insert(int element){
+		heap.add(element);
+		int childIndex = heap.size() - 1;
+		int parentIndex = (childIndex - 1) / 2;
+
+        //up-heapify
+		while(childIndex > 0){
+			if(heap.get(childIndex) < heap.get(parentIndex)){
+				int temp = heap.get(childIndex);
+				heap.set(childIndex, heap.get(parentIndex));
+				heap.set(parentIndex, temp);
+				childIndex = parentIndex;
+				parentIndex = (childIndex - 1) / 2;
+			}else{
+				return;
+			}
+		}
+	}
+
+	int removeMin() {
+        int minValue=heap.get(0);
+        int lastIndex=heap.size()-1;
+        heap.set(0,heap.get(lastIndex));
+        heap.remove(heap.size()-1);
+
+        //down-Heapify
+        int index=0;
+        int minIndex=index;
+        int leftchildIndex=1;
+        int rightchildIndex=2;
+        while(leftchildIndex<heap.size()){
+
+            if(heap.get(leftchildIndex)<heap.get(minIndex)){
+                minIndex=leftchildIndex;
+            }
+            if(rightchildIndex<heap.size() && heap.get(rightchildIndex)<heap.get(minIndex)){
+                minIndex=rightchildIndex;  
+            }
+            if(minIndex==index){
+                break;
+            }
+            int temp=heap.get(index);
+            heap.set(index,heap.get(minIndex));
+            heap.set(minIndex,temp);
+            index=minIndex;
+            leftchildIndex=2*index+1;
+            rightchildIndex=2*index+2;
+
+        }
+
+        return minValue;
+	}
+
+}

PriorityQueueException.java

@@ -0,0 +1,10 @@
+package priorityQueues;
+
+public class PriorityQueueException extends Exception{
+
+	/**
+	 * 
+	 */
+	private static final long serialVersionUID = 1L;
+
+}

PriorityQueueUse.java

@@ -0,0 +1,31 @@
+package priorityQueues;
+
+public class PriorityQueueUse {
+
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+
+		MaxPriorityQueue maxpq=new MaxPriorityQueue();
+		int arr[]= {5,6,9,10,83,65,1};
+		for(int i=0;i<arr.length;i++) {
+			maxpq.insert(arr[i]);
+		}
+
+		while(!maxpq.isEmpty()) {
+			System.out.print(maxpq.removeMax()+" ");
+		}
+
+		System.out.println();
+
+		MinPriorityQueue minpq=new MinPriorityQueue();
+		int a[]= {5,6,9,10,83,65,1};
+		for(int i=0;i<a.length;i++) {
+			minpq.insert(a[i]);
+		}
+
+		while(!minpq.isEmpty()) {
+			System.out.print(minpq.removeMin()+" ");
+		}
+	}
+
+}