哈夫曼树和哈夫曼编码

#include <stdio.h>#include <stdlib.h>//二叉树的每一个节点struct t_node{int data;struct t_node *left;struct t_node *right;};//创建一棵哈夫曼树 struct t_node* create_huffman_tree(int datas[], int n){//用于创建n个二叉树节点struct t_node **huff_elems;//树的根struct t_node *p;//i,j做循环，m1,m2分别记录最小值和次小值下标 int i, m1, m2, j;//分配n个指针大小的空间huff_elems = (struct t_node**)calloc(n, sizeof(struct t_node*));//为每个指针分配空间，创建n个二叉树节点for(i = 0; i < n; i++){huff_elems[i] = (struct t_node*)malloc(sizeof(struct t_node));huff_elems[i]->data = datas[i];huff_elems[i]->left = huff_elems[i]->right = NULL;}//第一次会从所有元素里面找两个最小的，以后会从所有的元素和所有生成的子树中//寻找最小的两个，所以循环n-1次即可以循环完毕 for(i = 0; i < n-1; i++) {m1 = -1;//每次将m1设置成指向第一个非空的元素或子树//将m2设置成指向第二个非空的元素或子树 for(j = 0; j < n; j++){if(huff_elems[j] != NULL && m1 == -1){m1 = j;continue;}else if(huff_elems[j] != NULL){m2 = j;break;}}//将m1指向最小的那个值，m2指向第二小的那个值 for(j = m2; j < n; j++) { if(huff_elems[j] != NULL && huff_elems[j]->data < huff_elems[m1]->data) { m2 = m1;m1 = j; } else if(huff_elems[j] != NULL && huff_elems[j]->data < huff_elems[m2]->data) { m2 = j; } }//利用两个最小的值组成一个新的节点，节点权为两个权之和p = (struct t_node*)malloc(sizeof(struct t_node));p->left = huff_elems[m1];p->right = huff_elems[m2];p->data = huff_elems[m1]->data + huff_elems[m2]->data;huff_elems[m1] = p;huff_elems[m2] = NULL; }//释放n个指针大小的空间free(huff_elems); return p;}//打印哈夫曼树的权值int calc_weight(struct t_node *tree, int len){if(tree == NULL)return 0;else if(tree->left == NULL && tree->right == NULL)return tree->data*len;else return calc_weight(tree->left, len+1) + calc_weight(tree->right, len+1);}int main(){int test[] = {3, 9, 5, 12, 6, 15};struct t_node *tree = create_huffman_tree(test, 6);printf("%d/n",calc_weight(tree, 0)); return 0;}

说来惭愧，觉得哈夫曼树挺简单的，但是自己写起来，写了半天都写不对，最后还是参考别人的才写出来的。接着写哈夫曼编码。 

#include <stdio.h>#include <stdlib.h>//二叉树的每一个节点struct t_node{int data;struct t_node *left;struct t_node *right;};//创建一棵哈夫曼树 struct t_node* create_huffman_tree(int datas[], int n){//用于创建n个二叉树节点struct t_node **huff_elems;//树的根struct t_node *p;//i,j做循环，m1,m2分别记录最小值和次小值下标 int i, m1, m2, j;//分配n个指针大小的空间huff_elems = (struct t_node**)calloc(n, sizeof(struct t_node*));//为每个指针分配空间，创建n个二叉树节点for(i = 0; i < n; i++){huff_elems[i] = (struct t_node*)malloc(sizeof(struct t_node));huff_elems[i]->data = datas[i];huff_elems[i]->left = huff_elems[i]->right = NULL;}//第一次会从所有元素里面找两个最小的，以后会从所有的元素和所有生成的子树中//寻找最小的两个，所以循环n-1次即可以循环完毕 for(i = 0; i < n-1; i++) {m1 = -1;//每次将m1设置成指向第一个非空的元素或子树//将m2设置成指向第二个非空的元素或子树 for(j = 0; j < n; j++){if(huff_elems[j] != NULL && m1 == -1){m1 = j;continue;}else if(huff_elems[j] != NULL){m2 = j;break;}}//将m1指向最小的那个值，m2指向第二小的那个值 for(j = m2; j < n; j++) { if(huff_elems[j] != NULL && huff_elems[j]->data < huff_elems[m1]->data) { m2 = m1;m1 = j; } else if(huff_elems[j] != NULL && huff_elems[j]->data < huff_elems[m2]->data) { m2 = j; } }//利用两个最小的值组成一个新的节点，节点权为两个权之和p = (struct t_node*)malloc(sizeof(struct t_node));p->left = huff_elems[m1];p->right = huff_elems[m2];p->data = huff_elems[m1]->data + huff_elems[m2]->data;huff_elems[m1] = p;huff_elems[m2] = NULL; }//释放n个指针大小的空间free(huff_elems); return p;}//打印哈夫曼树的权值int calc_weight(struct t_node *tree, int len){if(tree == NULL)return 0;else if(tree->left == NULL && tree->right == NULL)return tree->data*len;else return calc_weight(tree->left, len+1) + calc_weight(tree->right, len+1);}//哈夫曼编码void huff_coding(struct t_node *tree, int len){int i;//用来记录路径的编码，二叉树深度不得超10 static int a[10];if(tree != NULL){//如果到达叶子节点，打印路径 if(tree->left == NULL && tree->right == NULL){printf("%d的编码是：", tree->data);for(i = 0; i < len; i++)printf("%d ", a[i]);printf("/n");}else{a[len] = 0;huff_coding(tree->left, len+1);a[len] = 1;huff_coding(tree->right, len+1);}}}int main(){int test[] = {1, 2, 3};struct t_node *tree = create_huffman_tree(test, 3);printf("%d/n",calc_weight(tree, 0)); huff_coding(tree, 0);return 0;}