给定n个权值作为n个叶子结点，构造一棵二叉树，若带权路径长度达到最小，称这样的二叉树为最优二叉树，也称为哈夫曼树(Huffman tree)。通过这个程序，可以实现哈弗曼树。-Given n as n weights leaf node, construct a binary tree, if the weighted path length to a minimum, said this is the optimal binary tree, also known as Huffman tre