堆排序

src/HeapSort.java

@@ -0,0 +1,43 @@
+/**
+ * 堆排序
+ */
+public class HeapSort {
+    private static void maxHeapDown(int[] a, int start, int end){
+        int father = start;
+        int child = 2 * father + 1; // 左孩子
+        while (child <= end){
+            if (child < end && a[child] < a[child + 1]){
+                child++;  // 如果右孩子大，将左孩子变为右孩子
+            }
+            if (a[father] >= a[child]){
+                break;
+            }else {
+                int tmp = a[father];
+                a[father] = a[child];
+                a[child] = tmp;
+            }
+            father = child;
+            child = 2 * father + 1;
+        }
+    }
+    private static void heapSortAsc(int[] a){
+        int i;
+        int n = a.length;
+        for (i = n / 2 -1; i >= 0; i--){  // 从最后一个非终端节点开始，逐个向上遍历
+            maxHeapDown(a, i, n-1);
+        }
+        for (i = n - 1; i > 0; i--){
+            int tmp = a[0];
+            a[0] = a[i];
+            a[i] = tmp;
+            maxHeapDown(a, 0, i-1);
+        }
+    }
+    public static void main(String[] args){
+        int[] a = {9,2,5,4,7,3,8,0,1,6};
+        heapSortAsc(a);
+        for (int i :a){
+            System.out.print(i + " ");
+        }
+    }
+}