C语言哈夫曼树编码及其解码

Question

问题：
读取文件并对其中的数据进行哈夫曼树编码和解码
出现的问题：
用数据创建哈夫曼树并对哈夫曼树进行先序遍历的时候，出现程序崩溃，崩溃的原因我觉得莫名其妙
如图：

需求：
1.解决上述问题，将字符数据翻译为哈夫曼树编码
2.完成对解码部分的代码
代码：

#define _CRT_SECURE_NO_WARNINGS
#include "stdio.h"
#include "stdlib.h"
typedef struct TreeNode  //定义树结点
{
    int weight;  //权值
    int parent;
    int lchild;
    int rchild;
    char ch;
}treenode;

typedef struct HuffmanTree  //定义huffmantree，用数组表示树
{
    treenode* data;
    int length;
}huffmantree;

huffmantree* huffmantree_create(int weight[], int length, char character[])//huffmantree初始化
{
    huffmantree* tree = (huffmantree*)malloc(sizeof(huffmantree));
    tree->data = (treenode*)malloc(sizeof(treenode) * (2 * length - 1));  //n个元素，树中有2n-1个结点
    tree->length = length;
    for (int i = 0; i < length; i++)
    {
        tree->data[i].weight = weight[i];
        tree->data[i].parent = 0;
        tree->data[i].lchild = -1;
        tree->data[i].rchild = -1;
        tree->data[i].ch = character[i];
    }
    return tree;
}

int* selectMin(huffmantree* tree)//选择最小的两个结点
{
    int min=10000, secmin=10000;
    int minIndex, secminIndex;
    for (int i = 0; i < tree->length; i++)  //找到最小的结点的索引下标
    {
        if (tree->data[i].parent == 0)
        {
            if (tree->data[i].weight < min)
            {
                min = tree->data[i].weight;
                minIndex = i;
            }
        }
    }
    for (int i = 0; i < tree->length; i++)  //找到第二小的结点的索引下标
    {
        if (tree->data[i].parent == 0 && i != minIndex)
        {
            if (tree->data[i].weight < secmin)
            {
                secmin = tree->data[i].weight;
                secminIndex = i;
            }
        }
    }
    int* res = (int*)malloc(sizeof(int) * 2);  //返回两个数据，用int数组返回
    res[0] = minIndex;
    res[1] = secminIndex;
    return res;
}

void createTree(huffmantree* tree)  //建树
{
    int min;
    int secmin;
    int* res;
    for (int i = tree->length; i < tree->length * 2 - 1; i++)
    {
        res = selectMin(tree);
        printf("%d %d\t", res[0], res[1]);
        min = res[0];
        secmin = res[1];
        tree->data[i].weight = tree->data[min].weight + tree->data[secmin].weight;
        tree->data[min].parent = i;  //设置双亲结点
        tree->data[secmin].parent = i;
        tree->data[i].parent = 0;
        tree->data[i].lchild = min;  //设置孩子结点
        tree->data[i].rchild = secmin;
        tree->length++;
    }
}

void preorder(huffmantree* tree,int index)
{
    while (index != -1)
    {
        printf("%c %d\n", tree->data[index].ch, tree->data[index].weight);
        preorder(tree, tree->data[index].lchild);
        preorder(tree, tree->data[index].rchild);
    }
}

int main()
{
    FILE* fp;
    char ch, str[100],character[100];
    int length = 0, option, lengthchar = 0, weight[100];
    fp = fopen("test3.txt", "r+");
    if (fp == NULL)
    {
        printf("打开文件失败\n");
        exit(0);
    }
    printf("打开文件成功\n");
    ch = fgetc(fp);
    while (ch != EOF)
    {
        str[length] = ch;
        length++;
        ch = fgetc(fp);
    }
    str[length] = '\0';
    printf("该文件的数据为:");
    puts(str);
    printf("请问你是要对文件进行加密还是进行解密？(输入1为加密，输入2为解密)");
    printf("我选择：");
    scanf("%d", &option);
    while (option != 1 && option != 2)
    {
        printf("你的输入有误，请重新输入！\n我选择：");
        scanf("%d", &option);
    }
    if (option == 1)  //对数据进行huffmantree编码
    {
        int status;
        huffmantree* hftree;
        for (int i = 0; i < length; i++)  //先把str中的每一个字符都单列出来放进数组character
        {
            status = 0;
            for (int t = 0; t < lengthchar; t++)
            {
                if (str[i] == character[t])
                {
                    status = 1;
                    break;
                }
            }
            if (status == 1)
                continue;
            character[lengthchar] = str[i];
            lengthchar++;
        }
        character[lengthchar] = '\0';
        printf("字符数组为:");
        puts(character);
        for (int i = 0; i < lengthchar; i++)  //将权值数组归0
        {
            weight[i] = 0;
        }
        for (int i = 0; i < lengthchar; i++)  //设置权值数组
        {
            for (int t = 0; t < length; t++)
            {
                if (str[t] == character[i])  //统计每个字符的出现次数
                    weight[i]++;
            }
        }
        printf("权值数组为:");
        for (int i = 0; i < lengthchar; i++)
            printf("%d ", weight[i]);
        printf("\n");
        hftree = huffmantree_create(weight, lengthchar, character);
        createTree(hftree);
        preorder(hftree,hftree->length-1);
    }
    if (option == 2)//对huffmantree编码进行解码
    {
        
    }
    fclose(fp);
    return 0;
}
谢谢！

Answer 1

因为有某次调用selectMin()函数时没有进54行那个分支，导致secminIndex没有初始化就赋值给了res[1]