问题

我有一个课堂作业，需要读取一个txt文件并**显示**，**添加**和**删除**键（整数）和值（字符串）。

我想为每个键值对使用一个动态数组（我的教授说如果我这样做可以获得额外的学分）。目前，这是我的代码，我读取了txt文件并将其添加到数组中。

1. 我不确定是否需要创建一个足够存储任何单词的字符串，然后将其复制到更小的char中以减少内存使用(`strcpy(savStr, userStr);`)
2. 我不确定我是否正确地使用动态数组，或者如何添加更多索引
3. 我不确定我是否正确地向数组添加内存

int main(int argc, char **argc) {
// ... （你的代码保持不变）
}

这是txt文件

1,one
2,two
3,three
4,four
5,five
6,six
7,seven

这是添加到数组中的内容

1 - ottffsseven
2 - ttffsseven
3 - tffsseven
4 - ffsseven
5 - fsseven
6 - sseven
7 - seven

<details>
<summary>英文:</summary>

I have a class assignment where I need to take a txt file and **display**, **add**, and **remove** keys (int) and values (strings).

I would like to use a dynamic array for each (my professor said I can get extra credit if I do). Currently, this is what I have, I read the txt file and I add them to the array.

 1. I don&#39;t know if creating a string with enough memory for any word and then copying it to a smaller char for less memory is needed (`strcpy(savStr, userStr);`)
 2. I am not sure if I am doing the dynamic array correctly or how to add more indexes
 3. I dont know if I am adding the memory to the array correctly

int main(int argc, char **argc) {
int userNumber; //to take in user key and key in file
char userStr[1000]; //initial string to take value from user and string
int strL = 1; //find string length of value to find correct memory need to allocate
char savStr[strL]; //value with memory allocate for the size of the string
FILE *fp;
fp = fopen("values.txt", "r");
int *keyArry;
keyArry = (int *)calloc(8, sizeof(int));
char *valueArry;
valueArry = (char *)calloc(8, sizeof(char));
int curr = 0;

while (fscanf(fp, "%d,%s", &userNumber, userStr) != EOF) {
    strL = strlen(userStr);
    savStr[strL];
    strcpy(savStr, userStr);
    printf("%d - %s \n", cuserNumber, savStr);
    keyArry[curr] = userNumber;
    strcpy(&valueArry[curr], &savStr);
    curr++;
}
fclose(fp);
for (int i = 0; i < 7; i++) {
    printf("%d - %s \n", keyArry[i], &valueArry[i]);
}

this is the txt file

1,one
2,two
3,three
4,four
5,five
6,six
7,seven

this is the what is added to the array

1 - ottffsseven
2 - ttffsseven
3 - tffsseven
4 - ffsseven
5 - fsseven
6 - sseven
7 - seven

</details>


# 答案1
**得分**: 1

这段代码存在未定义行为，因为`char savStr[strL];`定义了一个`char`数组，长度为1，只足够存储空字符串。将任何较大的内容复制到它会导致未定义的行为。应该使用`char savStr[1000];`代替。在阅读完代码的其余部分后，似乎根本不需要这个额外的数组。

另外要注意的是，`char *valueArry;`定义了一个`char`指针，你将其初始化为指向一个包含8个`char`的数组。你应该改为定义一个指向`char *`数组的指针，并进行正确的初始化。

你的教授希望你使用动态数组，因此如果要存储的元素数量超过了分配的长度，可能需要重新分配它们。

以下是修改后的版本：

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

int main(int argc, char **argv) {
    int userNumber;     // 用于接收用户输入的键和文件中的键
    char userStr[1000]; // 用于接收用户输入的值和字符串
    FILE *fp = fopen("values.txt", "r");
    if (fp == NULL) {
        fprintf(stderr, "无法打开文件 values.txt: %s\n", strerror(errno));
        return 1;
    }
    int size = 8;
    int curr = 0;
    int *keyArry = calloc(size, sizeof(*keyArry));
    char **valueArry = calloc(size, sizeof(*valueArry));
    if (keyArry == NULL || valueArry == NULL) {
        fprintf(stderr, "无法分配数组\n");
        return 1;
    }

    while (fscanf(fp, "%d,%999s", &userNumber, userStr) == 2) {
        if (curr >= size) {
            // 必须重新分配数组
            size += size;
            keyArry = realloc(keyArry, size * sizeof(*keyArry));
            valueArry = realloc(valueArry, size * sizeof(*valueArry));
            if (keyArry == NULL || valueArry == NULL) {
                fprintf(stderr, "无法重新分配数组\n");
                return 1;
            }
        }
        printf("%d - %s\n", userNumber, userStr);
        keyArry[curr] = userNumber;
        valueArry[curr] = strdup(userStr);
        curr++;
    }
    fclose(fp);
    for (int i = 0; i < curr; i++) {
        printf("%d - %s \n", keyArry[i], valueArry[i]);
    }
    return 0;
}

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

int main(int argc, char **argc) {
    int userNumber;     //to take in user key and key in file
    char userStr[1000]; //initial string to take value from user and string
    FILE *fp = fopen("values.txt", "r");
    if (fp == NULL) {
        fprintf(stderr, "cannot open file values.txt: %s\n", strerror(errno));
        return 1;
    }
    int size = 8;
    int curr = 0;
    int *keyArry = calloc(size, sizeof(*keyArray));
    char **valueArry = calloc(size, sizeof(*valueArry));
    if (keyArry == NULL || valueArry == NULL) {
        fprintf(stderr, "cannot allocate arrays\n");
        return 1;
    }

    while (fscanf(fp, "%d,%999s", &userNumber, userStr) == 2) {
        if (curr >= size) {
            // must reallocate the arrays
            size += size;
            keyArry = realloc(keyArry, size * sizeof(*keyArry);
            valueArry = realloc(valueArry, size * sizeof(*valueArry);
            if (keyArry == NULL || valueArry == NULL) {
                fprintf(stderr, "cannot reallocate arrays\n");
                return 1;
            }
        }
        printf("%d - %s\n", cuserNumber, userStr);
        keyArry[curr] = userNumber;
        valueArry[curr] = strdup(userStr);
        curr++;
    }
    fclose(fp);
    for (int i = 0; i < curr; i++) {
        printf("%d - %s \n", keyArry[i], &valueArry[i]);
    }
    return 0;
}