typedef struct {
char letter;
int weight;
int parent, left, right;
}Node, *HuffmanTree;
typedef char* HuffmanCode;
void CreateHuffmanTree(char* filename, HuffmanTree* HT, int* t) {
FILE* fp = NULL;
fopen_s(&fp, filename, "r");
int n = *t;
int count[128] = { 0 };
char ch;
//统计短文出现的字母个数n及字母出现次数
while ((ch = fgetc(fp)) != EOF) {
if(count[ch] == 0)
n++;
count[ch] += 1;
}
//申请Huffman树的空间，0号单元不用
(*HT) = (HuffmanTree)malloc(2 * n * sizeof(Node));
HuffmanTree p = *HT;
int i, j;
for (i = 0, j = 1; i < 128; i++) {
if (count[i] != 0) {
(p + j)->letter = i;
(p + j)->weight = count[i];
(p + j)->parent = 0;
(p + j)->left = 0;
(p + j)->right = 0;
j++;
}
}
for (j = n + 1; j < 2 * n; j++) {
(p + j)->letter = "";
(p + j)->weight = 0;
(p + j)->parent = 0;
(p + j)->left = 0;
(p + j)->right = 0;
}
//构建Huffman树
for (i = n + 1; i < 2 * n; i++) {
int s1, s2;
Select((*HT), i - 1, &s1, &s2);
(p + s1)->parent = (p + s2)->parent = i;
(p + i)->weight = (p + s1)->weight + (p + s2)->weight;
(p + i)->left = s1;
(p + i)->right = s2;
}
}
