给定n个权值作为n个叶子结点，构造一棵二叉树，若该树的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。由此得到的二进制前缀编码称为哈夫曼编码。
例如权w={5,29,7,8,14,23,3,11}，8个结点，构造的哈夫曼树如下图所示：

算法实现如下：

typedef struct {
    unsigned int weight;
    unsigned int parent;
    unsigned int lchild;
    unsigned int rchild;
}Node, *HuffmanTree;

typedef char **HuffmanCode;

//在huffmanTree[1...n-1]中选择parent为0，且weight最小的两个结点，分别是s1,s2
void Select(HuffmanTree& huffmanTree, int n,int &s1,int &s2)
{
    int min = 1;
    for(int i =1;i<=n;i++){
        if(huffmanTree[i].parent==0){
            min = i;
            break;
        }
    }
    for(int i =1;i<=n;i++){
        if(huffmanTree[i].parent==0){
            if(huffmanTree[i].weight<huffmanTree[min].weight){