算法二之树形选择排序

 public static void treeSelectionSort(int[] data) {
        //长度小于2，无需排序
        if(data.length<2){
            return;
        }
        
        int leafCount = 1;    //完全二叉树的叶子节点数
        //算出完全二叉树的叶子节点数
        while (leafCount < data.length) {
            leafCount *= 2;
        }

        int[] tree = new int[leafCount * 2];  //树，tree[0]不存储数据
        //data里面的值赋值到树叶子节点
        for (int i = 0; i < data.length; i++) {
            tree[tree.length - i - 1] = data[i];
        }
        //初始化没有赋值的树叶子结点，赋值叶子节点最小值
        for (int i = data.length; i < leafCount; i++) {
            tree[tree.length - i - 1] = Integer.MIN_VALUE;
        }

        //初始化，构建整棵树
        for (int i = tree.length - 1; i > 1; i -= 2) {
            tree[i / 2] = Math.max(tree[i], tree[i - 1]);
        }
        data[data.length-1] = tree[1];   //将树根节点赋值于data
        
        //继续寻找剩下的最大值，逆向存储，升序排序
        for (int i = data.length-2; i >=0; i--) {
   
            int maxIndex = tree.length - 1;  //树根值所在的叶子节点的位置
            //寻找树根值所在的叶子节点的位置
            while (tree[maxIndex] != tree[1]) {
                maxIndex--;
            }
            tree[maxIndex]=Integer.MIN_VALUE; //该叶子节点赋值最小值
            
            //调整树，根节点值最大
           while(maxIndex>1){
                //左叶子结点
                if (maxIndex % 2 == 0) {
                    tree[maxIndex / 2] = Math.max(tree[maxIndex] ,
                              tree[maxIndex + 1]);
                } else {
                    tree[maxIndex / 2] = Math.max(tree[maxIndex] ,
                              tree[maxIndex - 1]);
                }
                maxIndex/=2;//指向父节点
            }

            data[i] = tree[1];   //将树根节点赋值于data
        }
    }