求助！有关赫夫曼树的

#include<cstdio>
#include<cstdlib>
typedef struct{
    int weight;
    int flag;
    int parent,lchild,rchild;
}HTNode,*HuffmanTree;       //动态分配数组存储赫夫曼树

void Select(HuffmanTree HT, int num, int &s1, int &s2){
    //s1是最小值，s2是次小值
    int minx = 1<<30; int mminx = 1<<30;
    for(int i = 1; i <= num; ++i){
        if(HT[i].weight < minx && !HT[i].flag){
            mminx = minx; s2 = s1;
            minx = HT[i].weight; s1 = i;
        }
        else if(HT[i].weight < mminx && !HT[i].flag){
            mminx = HT[i].weight; s2 = i;
        }
    }
    HT[s1].flag = HT[s2].flag = -1;
}

 
int L,length;
void AllLength(HuffmanTree HT, int m){
    length++;
    if (!HT[m].lchild && !HT[m].rchild)
    {
        L += HT[m].weight * (length-1);
    }
    else{
        int m1 = HT[m].lchild;
        AllLength(HT,m1);
        length--;
        int m2 = HT[m].rchild;
        AllLength(HT,m2);
        length--;
    }
}

 

 
void HuffmanCoding(HuffmanTree &HT,int *w, int n,int m){
    //w存放n个字符的权值（均>0）,构造赫夫曼树HT
    HT = (HuffmanTree)malloc((m+1)*sizeof(HTNode));  //0号单元未用
    HuffmanTree p = HT + 1;
    for(int i = 1; i <= n; ++i,++p){
        p->weight = w[i];
        p->parent = p->lchild = p->rchild = p->flag = 0;
    }
    for(int i = n+1; i <= m; ++i,++p){
        p->weight = p->parent = p->lchild = p->rchild = p->flag = 0;
    }
    int s1,s2;
    for(int i = n + 1; i <= m; ++i){//建赫夫曼树
        //在HT[1..i-1]选择parent为0且weight最小的两个结点，其序号分别为s1和s2。
        Select(HT, i-1, s1, s2);
        HT[s1].parent = i; HT[s2].parent = i;
        HT[i].lchild = s1; HT[i].rchild = s2;
        HT[i].weight = HT[s1].weight + HT[s2].weight;
    }
}

 
int main(){
    int n;
    int w[1010];
    while(scanf("%d",&n)!=EOF){
        int m = 2 * n - 1;
        HuffmanTree T;
        for(int i = 1; i <= n; ++i){
            scanf("%d",&w[i]);
        }
        HuffmanCoding(T,w,n,m);
        length = L = 0;
        AllLength(T,m);
        free(T);
        printf("%d\n",L);
    }
    return 0;
}