0001 auto Larger = [](auto A, Rank n, Rank i) //A[i]两个孩子中的大者
0002    { return (RC(i) < n) && (A[LC(i)] < A[RC(i)]) ? RC(i) : LC(i); };
0003 template <typename T> void siftDown(T* A, const Rank n, Rank i) { //0 <= i < _size
0004    T e = A[i]; //下滤者先备份，然后让大的后代顺次上移
0005    for (Rank j;  (LC(i) < n) && (e < A[j = Larger(A, n, i)]);  A[i] = A[j], i = j);
0006    A[i] = e; //下滤者最终就位
0007 } //siftDown