Add priorityqueue code

Author: jbee37142

src/test/java/datastructure/priorityqueue/CalcTopTen.java

@@ -0,0 +1,72 @@
+package datastructure.priorityqueue;
+
+import org.junit.Test;
+
+import java.util.PriorityQueue;
+import java.util.Queue;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+public class CalcTopTen {
+
+    /*
+        TASK
+        많은 수 중 top 10을 구한다.
+     */
+
+    @Test
+    public void test() {
+        TopTen t = new TopTen();
+        t.put(1);
+        t.put(2);
+        t.put(3);
+        t.put(4);
+        t.put(5);
+        t.put(6);
+        t.put(7);
+        t.put(8);
+        t.put(9);
+        t.put(10);
+        t.put(11);
+        t.put(12);
+        t.put(19);
+        t.put(21);
+        t.put(13);
+        int[] arr = new int[10];
+        int j = 0;
+        for (int i = arr.length; i > 0; i--) {
+            arr[j] = i;
+            j++;
+        }
+        assertThat(t.getTop10(), is(arr));
+    }
+
+    public class TopTen {
+        private Queue<Integer> queue = new PriorityQueue<>();
+
+        private void put(int data) {
+            queue.add(data);
+        }
+
+        private int[] getTop10() {
+            int[] arr = new int[10];
+            for (int i = arr.length - 1; i >= 0; i--) {
+                arr[i] = queue.poll();
+            }
+            return arr;
+        }
+
+        private void read(int n) {
+            if (queue.size() < 10) {
+                queue.offer(n);
+            } else {
+                int tenth = queue.peek();
+                if (n > tenth) {
+                    queue.poll();
+                    queue.offer(n);
+                }
+            }
+        }
+    }
+}

src/test/java/datastructure/priorityqueue/HeapSortByUsingPQ.java

@@ -0,0 +1,47 @@
+package datastructure.priorityqueue;
+
+import org.junit.Test;
+
+import java.util.PriorityQueue;
+import java.util.Queue;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+public class HeapSortByUsingPQ {
+
+    /*
+        TASK
+        Priority queue를 사용하여 heap sort를 하라.
+     */
+
+    @Test
+    public void test() {
+        int[] arr = new int[5];
+        arr[0] = 3;
+        arr[1] = 7;
+        arr[2] = 1;
+        arr[3] = 9;
+        arr[4] = 6;
+
+        int[] sortedArr = new int[5];
+        sortedArr[0] = 1;
+        sortedArr[1] = 3;
+        sortedArr[2] = 6;
+        sortedArr[3] = 7;
+        sortedArr[4] = 9;
+        assertThat(heapSort(arr), is(sortedArr));
+    }
+
+    public int[] heapSort(int[] arr) {
+        Queue<Integer> queue = new PriorityQueue<>();
+        for (int i = 0; i < arr.length; i++) { //O(nlogn)
+            queue.add(arr[i]);
+        }
+        int[] newArr = new int[arr.length];
+        for (int i = 0; i < newArr.length; i++) { //O(nlogn)
+            newArr[i] = queue.poll();
+        }
+        return newArr;
+    }
+}