堆排序的实现。。闲的没事手撸了一个。。

    //HeapUtil.heapSort(arr) 

    class HeapUtil
    {
        public static void swap<T>(IList<T> list, int i, int j)
        {
            T tmp = list[i];
            list[i] = list[j];
            list[j] = tmp;
        }

        public static void adjustUp(IList<int> list, int idx)
        {
            int n = idx;
            while(n != 0)
            {
                int parent = (n - 1) / 2;

                if (list[n] < list[parent])
                {
                    swap(list, n, parent);
                    n = parent;
                }
                else
                    break;

            }
        }

        public static void adjustDown(IList<int> list, int idx)
        {
            int n = idx;
            while (n < list.Count / 2)
            {
                int lchild = n * 2 + 1;
                int smallest = n;
                if(list[lchild] < list[smallest])
                {
                    smallest = lchild;
                }

                int rchild = lchild + 1;
                if(rchild < list.Count && list[rchild] < list[smallest])
                {
                    smallest = rchild;
                }

                if (smallest == n)
                    break;
                else
                {
                    swap(list, smallest, n);
                    n = smallest;
                }

            }
        }

        public static void heapAdd(IList<int> list, int elem)
        {
            list.Add(elem);
            adjustUp(list, list.Count - 1);
        }

        public static int heapRm(IList<int> list, int idx)
        {
            swap(list, idx, list.Count - 1);
            int res = list[list.Count - 1];
            list.RemoveAt(list.Count - 1);
            adjustDown(list, idx);
            return res;

        }

        public static void heapMake(IList<int> list)
        {
            for(int i = list.Count / 2 - 1; i >= 0; i--)
            {
                adjustDown(list, i);
            }
        }

        public static void heapSort(IList<int> list)
        {
            heapMake(list);

            IList<int> res = new List<int>();

            while(list.Count != 0)
            {
                res.Add(heapRm(list, 0));
            }

            list.Clear();
            foreach(var e in res) list.Add(e);

        }


    }