c - 程序适用于字符串文字，但不适用于字符串数组

Question

我有一个哈希表 ADT，它有两个函数:插入和查找。我将哈希表、哈希表大小、ID # 和书名放入插入函数中，然后将其插入到哈希表中。当我向它传递字符串文字时，它工作得很好，即 insert(...,"Hello, world!"...); 当我从文件中读取字符串时，它不起作用，将它们存储在数组中，并尝试使用我的插入和查找函数。 我的所有代码都在这里，但最重要的文件是 main.c 和 hash.c。 Hash.c 具有 newHash()、hash()、insert() 和 Lookup() 函数，main.c 从两个文件(在本例中为 test1.lib.in 和 test1.req.in)读取，并从第一个文件读取file 将从每一行获取一本书的图书馆 ID 和标题，然后将其放入哈希表中。从第二个文件中，它获取对书名的请求，并应在其链接列表中打印 id。

• 文件链接列表 https://docs.google.com/document/d/1tFNs-eVkfnCfjwAHcAUdHtUl1KVv_WcnW2IS0SRFvcM/edit?usp=sharing

有效的代码示例。

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include "list.h"
#include "hash.h"

int main(){
    ListHndl* temp = newHash(10);
    insert(442440, "cvyaqbznxel", 10,temp);
    lookup(temp,"cvyaqbznxel", 10);
    return 0;
}

无效的代码

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include "list.h"
#include "hash.h"


int main(int argc, char * argv[]) {

    if (argc != 3) {
        printf("Incorrect arguments, please specify 2 files to be read\n");
        return EXIT_FAILURE;
    }
    FILE *file = fopen( argv[1], "r");
    FILE *secondFile = fopen(argv[2], "r");
    if (file == 0 || secondFile == 0) {
        printf("Could not open a file\n");
        return EXIT_FAILURE;
    }
    int numDataLines2;
    int numDataLines;
    int hashTableSize;
    //First line of first file gives number of lines in file and 
    //size of hash table to be made
    if(fscanf(file, "%d%d", &numDataLines, &hashTableSize) < 2) {
        printf("Unable to parse first line of first file\n");
        return EXIT_FAILURE;
    } 
    ListHndl* theHash = newHash(hashTableSize);
    int libraryID;
    char *tempString = calloc(numDataLines,41*sizeof(char));
    char lineHolder[129];
    //discard the new line which always shows up
    fgets(lineHolder, 128, file);
    for(int i = 0; i < numDataLines; i++) {
        //Gets the whole line to be scanned with sscanf
        fgets(lineHolder, 128, file);

        //If the line consists of just a newline char, continue
        if(strcmp(lineHolder, "\n") == 0 ) {
            continue;
        }
        //Scans the line retrieved from fgets and placed in lineHolder
        if(sscanf(lineHolder, "%d, %40[^\n]", &libraryID,&tempString[i]) == 0){
            printf("Unable to parse line %d of first file\n",i+2);
            return EXIT_FAILURE;
        }
        insert(libraryID, &tempString[i], hashTableSize, theHash);
    }
    char String[41];
    fgets(String, 40, secondFile);
    numDataLines2 = atoi(String);
    char *storeSecondFileStuff = calloc(numDataLines2,41*sizeof(char));
    for(int i = 0; i< numDataLines2; i++) {
        fgets(lineHolder, 128, secondFile);
        if(strcmp(lineHolder, "\n") == 0) {
            continue;
        }
        if(sscanf(lineHolder, "%40[^\n]",&storeSecondFileStuff[i]) == 0) {
            printf("Unable to parse line %d of second file\n",i+2);
            return EXIT_FAILURE;
        }
        lookup(theHash, &storeSecondFileStuff[i], hashTableSize);
    }
    printf("\n");
    fclose(file);
    fclose(secondFile);
    return 0;
}

谢谢!

Answer 1

我认为您有多个问题。首先，您可能没有正确扫描输入行。更改线路

 if(sscanf(lineHolder, "%d, %40[^\n]", &libraryID,&tempString[i]) == 0)

至

 if(sscanf(lineHolder, "%d, %40[^\n]", &libraryID, tempString) < 0)

这样，你就会陷入sscanf的情况函数未成功转换两个参数 - 例如，如果输入行中没有逗号。请注意sscanf返回成功转换的次数；成功将返回值 2 ，因此测试 <2这是正确的方法。

另请注意，我更改了 &tempString[i]至tempString 。前者指向 tempString 沿线的某个地方- 只分配了 41 个字符。然而，您总是允许最多写入 40 个字符(加上 '\0' ) - 因此您将写入超过字符串末尾的内容。由于这只是一个临时变量，因此这样做没有任何意义。只需扫描输入进入临时变量，然后用它做任何你需要做的事情。

这意味着您的 insert也发生变化，从

    insert(libraryID, &tempString[i], hashTableSize, theHash);

至

    insert(libraryID, tempString, hashTableSize, theHash);

同样，您需要在代码中做同样的事情。

这里尝试让代码为您工作 - 看看这是否合适。请注意，我真正所做的只是更改 tempString 的类型和storeSecondFileStuff ，并相应地修改了它们在各种函数调用中的使用方式。由于涉及的其他文件的复杂性，我没有尝试编译/运行 - 但这应该会有所帮助:

int main(int argc, char * argv[]) {

    if (argc != 3) {
        printf("Incorrect arguments, please specify 2 files to be read\n");
        return EXIT_FAILURE;
    }
    FILE *file = fopen( argv[1], "r");
    FILE *secondFile = fopen(argv[2], "r");
    if (file == 0 || secondFile == 0) {
        printf("Could not open a file\n");
        return EXIT_FAILURE;
    }
    int numDataLines2;
    int numDataLines;
    int hashTableSize;
    //First line of first file gives number of lines in file and 
    //size of hash table to be made
    if(fscanf(file, "%d%d", &numDataLines, &hashTableSize) < 2) {
        printf("Unable to parse first line of first file\n");
        return EXIT_FAILURE;
    } 
    ListHndl* theHash = newHash(hashTableSize);
    int libraryID;
    char **tempString = calloc(numDataLines,sizeof(char*));  // <<< ARRAY of pointers
    char lineHolder[129];
    //discard the new line which always shows up
    fgets(lineHolder, 128, file);
    for(int i = 0; i < numDataLines; i++) {
        //Gets the whole line to be scanned with sscanf
        fgets(lineHolder, 128, file);
        tempString[i] = calloc(1, 41 * sizeof(char)); // <<< space for this string
        //If the line consists of just a newline char, continue
        if(strcmp(lineHolder, "\n") == 0 ) {
            continue;
        }
        //Scans the line retrieved from fgets and placed in lineHolder
        if(sscanf(lineHolder, "%d, %40[^\n]", &libraryID, tempString[i]) < 0){ // <<< changed
            printf("Unable to parse line %d of first file\n",i+2);
            return EXIT_FAILURE;
        }
        insert(libraryID, tempString[i], hashTableSize, theHash); // <<< changed
    }
    char String[41];
    fgets(String, 40, secondFile);
    numDataLines2 = atoi(String);
    char **storeSecondFileStuff = calloc(numDataLines2, sizeof(char*)); // changed: again char **
    for(int i = 0; i< numDataLines2; i++) {
        fgets(lineHolder, 128, secondFile);
        storeSecondFileStuff[i] = calloc(1, 41 * sizeof(char));
        if(strcmp(lineHolder, "\n") == 0) {
            continue;
        }
        if(sscanf(lineHolder, "%40[^\n]",storeSecondFileStuff[i]) == 0) {
            printf("Unable to parse line %d of second file\n",i+2);
            return EXIT_FAILURE;
        }
        lookup(theHash, storeSecondFileStuff[i], hashTableSize); // <<<< changed
    }
    printf("\n");
    fclose(file);
    fclose(secondFile);
    return 0;
}