c语言实现构建huffman树算法

下面是用C语言实现构建Huffman树算法的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_SIZE 1000

// 定义Huffman树节点结构体
typedef struct {
    int weight; // 权值
    int parent; // 父节点下标
    int left;   // 左子节点下标
    int right;  // 右子节点下标
} HuffNode, *HuffTree;

// 定义Huffman编码结构体
typedef struct {
    char ch;        // 字符
    char code[MAX_SIZE]; // 编码
} HuffCode, *HuffCodeTable;

// 选择权值最小的两个节点
void select(HuffTree tree, int n, int *s1, int *s2) {
    int i;
    int min1, min2;
    min1 = min2 = MAX_SIZE;

    // 找出第一个权值最小的节点
    for (i = 0; i < n; i++) {
        if (tree[i].weight < min1 && tree[i].parent == -1) {
            min1 = tree[i].weight;
            *s1 = i;
        }
    }

    // 找出第二个权值最小的节点
    for (i = 0; i < n; i++) {
        if (tree[i].weight < min2 && tree[i].parent == -1 && i != *s1) {
            min2 = tree[i].weight;
            *s2 = i;
        }
    }
}

// 构建Huffman树
void buildHuffTree(HuffTree tree, int n) {
    if (n <= 1) return;

    int i, s1, s2;
    for (i = 0; i < 2 * n - 1; i++) {
        tree[i].parent = -1;
        tree[i].left = -1;
        tree[i].right = -1;
    }

    // 构建n-1个节点的Huffman树
    for (i = n; i < 2 * n - 1; i++) {
        select(tree, i, &s1, &s2);
        tree[s1].parent = i;
        tree[s2].parent = i;
        tree[i].left = s1;
        tree[i].right = s2;
        tree[i].weight = tree[s1].weight + tree[s2].weight;
    }
}

// 获取Huffman编码
void getHuffCode(HuffTree tree, HuffCodeTable table, int n) {
    int i, j;
    char *code = (char *)malloc(n * sizeof(char));
    code[n - 1] = '\0';

    for (i = 0; i < n; i++) {
        int start = n - 1;
        int c = i;
        int p = tree[c].parent;
        while (p != -1) {
            if (tree[p].left == c) {
                code[--start] = '0';
            } else {
                code[--start] = '1';
            }
            c = p;
            p = tree[c].parent;
        }
        strcpy(table[i].code, &code[start]);
    }
    free(code);
}

int main() {
    int n;
    printf("输入字符个数：");
    scanf("%d", &n);

    // 输入字符及其权值
    HuffTree tree = (HuffTree)malloc(sizeof(HuffNode) * (2 * n - 1));
    HuffCodeTable table = (HuffCodeTable)malloc(sizeof(HuffCode) * n);
    int i;
    for (i = 0; i < n; i++) {
        printf("输入第%d个字符及其权值：", i + 1);
        scanf("%s %d", &table[i].ch, &tree[i].weight);
    }

    // 构建Huffman树
    buildHuffTree(tree, n);

    // 获取Huffman编码
    getHuffCode(tree, table, n);

    // 输出Huffman编码
    printf("Huffman编码如下：\n");
    for (i = 0; i < n; i++) {
        printf("%c: %s\n", table[i].ch, table[i].code);
    }

    free(tree);
    free(table);
    return 0;
}

这段代码实现了从用户输入字符及其权值，构建Huffman树，获取Huffman编码，输出Huffman编码的功能。在构建Huffman树时，采用的是贪心策略，每次选择权值最小的两个节点进行合并。在获取Huffman编码时，采用的是自底向上的遍历方式，从叶子节点到根节点依次获取每个字符的编码。