update MaxHeap

README.md

@@ -50,3 +50,4 @@
 
 ### 优先队列和堆
 1. [堆的基本定义](https://github.com/l81893521/basic-data-structure/blob/master/src/main/java/will/zhang/heap/AMaxHeap.java)
+1. [往堆中添加元素和siftUp](https://github.com/l81893521/basic-data-structure/blob/master/src/main/java/will/zhang/heap/BMaxHeap.java)

src/main/java/will/zhang/heap/Array.java

@@ -104,6 +104,20 @@ public void add(int index, T e){
 
     }
 
+    /**
+     * 交换索引i和索引j的元素
+     * @param i
+     * @param j
+     */
+    public void swap(int i, int j){
+        if(i < 0 || j < 0 || i >= size || j >= size){
+            throw new IllegalArgumentException("Index is illegal");
+        }
+        T t = data[i];
+        data[i] = data[j];
+        data[j] = t;
+    }
+
     @Override
     public String toString(){
         StringBuilder builder = new StringBuilder();

src/main/java/will/zhang/heap/BMaxHeap.java

@@ -0,0 +1,87 @@
+package will.zhang.heap;
+
+/**
+ * 使用数组实现最大堆
+ * @param <E>
+ */
+public class BMaxHeap<E extends Comparable<E>> {
+
+    //存放数据
+    private Array<E> data;
+
+    public BMaxHeap(int capacity){
+        data = new Array<>(capacity);
+    }
+
+    public BMaxHeap(){
+        data = new Array<>();
+    }
+
+    /**
+     * 获取堆的大小
+     * @return
+     */
+    public int size(){
+        return data.getSize();
+    }
+
+    /**
+     * 返回堆是否为空
+     * @return
+     */
+    public boolean isEmpty(){
+        return data.isEmpty();
+    }
+
+    /**
+     * 返回父亲节点的索引
+     * @param index
+     * @return
+     */
+    private int parent(int index){
+        if(index == 0){
+            throw new IllegalArgumentException("index-0 doesn't have parent.");
+        }
+        return (index - 1) / 2;
+    }
+
+    /**
+     * 返回左孩子节点的索引
+     * @param index
+     * @return
+     */
+    private int leftChild(int index){
+        return index * 2 + 1;
+    }
+
+    /**
+     * 返回右孩子节点的索引
+     * @param index
+     * @return
+     */
+    private int rightChild(int index){
+        return index * 2 + 2;
+    }
+
+    /**
+     * 向堆中添加元素
+     * @param e
+     */
+    public void add(E e){
+        data.addLast(e);
+        siftUp(data.getSize() - 1);
+    }
+
+    /**
+     * 堆的核心方法, 元素上浮至适当位置(符合堆的定义的位置, 比父亲节点小并且比孩子节点大)
+     * @param k
+     */
+    private void siftUp(int k) {
+        //如果当前k比父亲节点parent(k)大, 则交换位置
+        while(k > 0 && data.get(parent(k)).compareTo(data.get(k)) < 0){
+            data.swap(k, parent(k));
+            k = parent(k);
+        }
+    }
+
+}