给定一个数字数组，返回哈夫曼树的头指针？

struct BTreeNode* CreateHuffman(ElemType a[], int n){int i, j;struct BTreeNode **b, *q;b = malloc(n*sizeof(struct BTreeNode));for (i = 0; i < n; i++){b[i] = malloc(sizeof(struct BTreeNode));b[i]->data = a[i];b[i]->left = b[i]->right = NULL;}for (i = 1; i < n; i++){int k1 = -1, k2;for (j = 0; j < n; j++){if (b[j] != NULL && k1 == -1){k1 = j;continue;}if (b[j] != NULL){k2 = j;break;}}for (j = k2; j < n; j++){if (b[j] != NULL){if (b[j]->data < b[k1]->data){k2 = k1;k1 = j;}else if (b[j]->data < b[k2]->data)k2 = j;}}q = malloc(sizeof(struct BTreeNode));q->data = b[k1]->data + b[k2]->data;q->left = b[k1];q->right = b[k2];b[k1] = q;b[k2] = NULL;}free(b);return q;}