some quick help in comparing 2 files using binary search - c

Question

so I wrote this code for a project, and I thought it'd work, but it was only doing a comparison for the very first term from one of my files(the IkeaWords.txt file).
Where did I go wrong?
so this is what I wrote hopefully it's enough.
/*Display each IKEA product name that can be found in the English dictionary.
The full list of the 1764 unique IKEA product words is in IKEAwords.txt
To see if words exist in English, use the 40,444 word English dictionary dictionary.txt,
where the longest word has 21 characters. To lookup a word in the dictionary consider
using binary search,
Print out each word that is found.
*/
#define _CRT_SECURE_NO_WARNINGS
#define NumberOfWordsInDictionary 40437
#define MaxWordSize 21+1
#define NumberOfWordsInIkea 1764
#include <stdio.h>
#include <string.h> // for string length
#include <stdlib.h> // for exit()
// Maximum size of any word in the dictionary, + 1 for null
const char DictionaryFileName[] = "dictionary.txt"; // File name for where dictionary words are found
const char IkeaFileName[] = "IKEAwords.txt";
//--------------------------------------------------------------------------------------
// Use binary search to look up the word from the .txt file in the dictionary array,
//returning index if found, -1 otherwise
int binarySearch(const char ikeaWord[][MaxWordSize], // word to be looked up
const char dictionary[][MaxWordSize], // the dictionary of words
int numberOfDictionaryWords //number of words in the dictionary
)
{
int low, mid, high; // array indices for binary search
int searchResult = -1; // Stores index of word if search succeeded, else -1
// Binary search for word
low = 0;
high = numberOfDictionaryWords - 1;
int i = 0;
while (i < MaxWordSize)
{
while (low <= high)
{
mid = (low + high) / 2;
// searchResult negative value means word is to the left, positive value means
// word is to the right, value of 0 means word was found
searchResult = strcmp(ikeaWord[i], dictionary[mid]);
if (searchResult == 0) {
// Word IS in dictionary, so return the index where the word was found
return mid;
}
else if (searchResult < 0)
{
high = mid - 1; // word should be located prior to mid location
}
else
{
low = mid + 1; // word should be located after mid location
}
}
i++;
}
// Word was not found
return -1;
}//end binarySearch()
//--------------------------------------------------------------------------------------
// Read in the words from the dictionary file
void readWordsInFromDictionaryFile(FILE *pInputFile, char dictionary[][MaxWordSize])
{
int index = 0; // index of dictionary word being read
int maxWordLength = 0;
// Associate the actual file name with file pointer and try to open it
pInputFile = fopen(DictionaryFileName, "r");
// verify that file open worked
if (pInputFile == NULL) {
printf("Can't open %s. Verify it is in correct location\n", DictionaryFileName);
exit(-1);
}
// Keep reading words while there are any
while (fscanf(pInputFile, "%s", dictionary[index]) != EOF) {
int tempLength = (int)strlen(dictionary[index]);
if (tempLength > maxWordLength) {
maxWordLength = tempLength;
}
index++;
}
// uncomment out code test array dictionary[][]
//printf("There were %d words in the dictionary, with max length %d. \n", index, maxWordLength);
fclose(pInputFile); // close the dictionary file
printf("There were %d words read from the dictionary with max length %d.\n", index, maxWordLength);
}//end readInputFile()
void readWordsInFromIkeaFile(FILE *pInputFile2, char ikeaWord[][MaxWordSize])
{
int index2 = 0; // index of dictionary word being read
int maxIkeaWordLength = 0;
// Associate the actual file name with file pointer and try to open it
pInputFile2 = fopen(IkeaFileName, "r");
// verify that file open worked
if (pInputFile2 == NULL)
{
printf("Can't open %s. Verify it is in correct location\n", IkeaFileName);
exit(-1);
}
// Keep reading words while there are any
while (fscanf(pInputFile2, "%s", ikeaWord[index2]) != EOF)
{
int tempLength2 = (int)strlen(ikeaWord[index2]);
if (tempLength2 > maxIkeaWordLength)
{
maxIkeaWordLength = tempLength2;
}
index2++;
}
printf("There were %d words read from the Ikea file with max length %d.\n", index2,maxIkeaWordLength);
}
//--------------------------------------------------------------------------------------
int main()
{
char dictionary[NumberOfWordsInDictionary][MaxWordSize];
char ikeaWord[NumberOfWordsInIkea][MaxWordSize];
FILE *pInputFile = fopen(DictionaryFileName, "r"); // file pointer
FILE *pInputFile2 = fopen(IkeaFileName, "r");
readWordsInFromDictionaryFile(pInputFile, dictionary);
readWordsInFromIkeaFile(pInputFile2, ikeaWord); // used as input
// Find index of word in dictionary
int index = -1;
int j = 0; // counter
while(j<NumberOfWordsInIkea)
{
index = binarySearch(ikeaWord[j], dictionary, NumberOfWordsInDictionary);
// Display results
if (index != -1)
{
// word was found, so display it
printf("The word \"%s\" was found.\n", dictionary[index]);
}
j++;
}
system("pause");
return 0;
}
I wrote it in visual studio 2015 if you need to know that too.
Thanks for the help!

Answer 1

You have several errors and unnecessary things in your code. I took the liberty to change some things to make it work (you might have already found them if you followed the hints in the comments) and some things to make it a bit cleaner (non compiler warnings from GCC). Did not check with MSVS because of lack of MSVS.
#define _CRT_SECURE_NO_WARNINGS
// changed values to accomodate different data-files sizes
#define NumberOfWordsInDictionary 99172
#define MaxWordSize 64
#define NumberOfWordsInIkea 1393
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
// from /usr/dict/words (put to lower case)
const char DictionaryFileName[] = "words.txt";
// scraped from http://lar5.com/ikea/ (put to lower case)
const char IkeaFileName[] = "ikea_names.txt";
// ripped 'const' and changed ikeaWord[][] to take a the single entry
int binarySearch(char *ikeaWord, char dictionary[][MaxWordSize],
int numberOfDictionaryWords)
{
int low, mid, high;
int searchResult = -1;
low = 0;
high = numberOfDictionaryWords - 1;
// ripped outer loop because we search for Ikea names one by one
while (low <= high) {
mid = (low + high) / 2;
searchResult = strcmp(ikeaWord, dictionary[mid]);
if (searchResult == 0) {
return mid;
} else if (searchResult < 0) {
high = mid - 1;
} else {
low = mid + 1;
}
}
return -1;
}
int readWordsInFromDictionaryFile(FILE * pInputFile,
char dictionary[][MaxWordSize])
{
int index = 0;
int maxWordLength = 0;
// ripped fopen() because that happened already in main()
// Changed from fscanf to fgets because the *scanf() family is a
// never ending source of problems, see stackoverflow et al. for endless examples
while (fgets(dictionary[index], MaxWordSize - 1, pInputFile)) {
int tempLength = (int) strlen(dictionary[index]);
// Because of the change from fscanf to fgets we need to snip the newline off
// (for "\r\n" endings snipp two)
dictionary[index][tempLength - 1] = '\0';
if (tempLength > maxWordLength) {
maxWordLength = tempLength;
}
index++;
}
// If fgets returns NULL it is either EOF or an error
if (ferror(pInputFile)) {
fprintf(stderr, "something bad happend while reading dictionary\n");
return 0;
}
fclose(pInputFile);
printf("There were %d words read from the dictionary with max length %d.\n",
index, maxWordLength);
return 1;
}
// snipped off the addition of "2" to the variable names, no need for that
int readWordsInFromIkeaFile(FILE * pInputFile, char ikeaWord[][MaxWordSize])
{
int index = 0;
int maxIkeaWordLength = 0;
while (fgets(ikeaWord[index], MaxWordSize - 1, pInputFile)) {
int tempLength = (int) strlen(ikeaWord[index]);
ikeaWord[index][tempLength - 1] = '\0';
if (tempLength > maxIkeaWordLength) {
maxIkeaWordLength = tempLength;
}
index++;
}
if (ferror(pInputFile)) {
fprintf(stderr, "something bad happend while reading ikeawords\n");
return 0;
}
printf("There were %d words read from the Ikea file with max length %d.\n",
index, maxIkeaWordLength);
return 1;
}
//--------------------------------------------------------------------------------------
int main()
{
char dictionary[NumberOfWordsInDictionary][MaxWordSize];
char ikeaWord[NumberOfWordsInIkea][MaxWordSize];
int res;
// added error-checks
FILE *pInputFile = fopen(DictionaryFileName, "r");
if (pInputFile == NULL) {
fprintf(stderr, "Can't open %s. Verify it is in correct location\n",
DictionaryFileName);
exit(EXIT_FAILURE);
}
FILE *pInputFile2 = fopen(IkeaFileName, "r");
if (pInputFile2 == NULL) {
fprintf(stderr, "Can't open %s. Verify it is in correct location\n",
IkeaFileName);
exit(EXIT_FAILURE);
}
if ((res = readWordsInFromDictionaryFile(pInputFile, dictionary)) == 0) {
fprintf(stderr, "Error in reading dictionary\n");
exit(EXIT_FAILURE);
}
if ((res = readWordsInFromIkeaFile(pInputFile2, ikeaWord)) == 0) {
fprintf(stderr, "Error in reading ikea-file\n");
exit(EXIT_FAILURE);
}
int index = -1;
int j = 0;
while (j < NumberOfWordsInIkea) {
index = binarySearch(ikeaWord[j], dictionary, NumberOfWordsInDictionary);
if (index != -1) {
printf("The word \"%s\" was found.\n", dictionary[index]);
}
j++;
}
// Seems to be useful when run in MS-Windows
#if defined _WIN32 || defined WIN32 || defined WIN64 || defined _WIN64
sytem("pause");
#endif
exit(EXIT_SUCCESS);
}
I did not polish every corner, it still needs some work. For example: the two functions reading the two files are actually doing the same, just for a different file and a different dictionary. That can be done with a single function. The name of the files, the lengths of the file, and the length of the entries of these files are fixed, they can be made dynamic to be able to use different input without recompiling.
But all over: not bad for start!