"Overwrite" repeated values in a file (C) [closed] - c

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Hello i have a little problem, and i cannot find a solution yet. I have a file (data.txt) with the next information:
5,5,6,2,5,2
1,4,2,3,7,2
4,2,5,2,3,4
5,5,6,2,5,2
4,5,2,6,2,4
2,1,5,6,3,2
And i want to set to 0 all the repeated lines, for example: 5,5,6,2,5,2 appears two times, so the final file must look as follows:
0,0,0,0,0,0
1,4,2,3,7,2
4,2,5,2,3,4
0,0,0,0,0,0
4,5,2,6,2,4
2,1,5,6,3,2
I have tried with auxiliar files but cannot get the solution, i would be so apreciated with any help.
I can set any of the two lines to 0 but not both of them, and the same if the same line appears more than twice.

Answer 1

You can achieve that by:
Opening the input/output file on "r+" mode first
Systematically getting characters from the file line by line into an array of character arrays
Comparing lines with each other, setting characters other than commas to zero characters when they are paired
Seeking back in the file
Writing lines back into the file, separating them with new lines
To detect pairings properly, you could possibly follow the following logic:
Pick a line, create a variable along with it and set it to 1
Compare that line with the others
In case of a match, set the variable to 0 and keep on comparing your line with the rest
... until the end, replacing the non-comma characters to zero characters with each match
After checking with them all, modify or don't modify your initially picked line depending on the state of that variable which you had set to 1 initially
Here's a code that works, should work without flaw unless you have insufficient memory:
#include <stdio.h>
#include <malloc.h>
#include <string.h>
void settozero( char * line ) {
for ( int i = 0; line[i] != '\0'; i++ )
if ( line[i] != ',' )
line[i] = '0';
}
int main( ) {
char ** lines = NULL;
FILE * input;
if ( ( input = fopen( "input", "r+" ) ) == NULL ) {
printf( "error at line %d", __LINE__ );
return -1;
}
int currentchar;
int newline = 1;
int linecount = 0;
int lineindex;
int linesize;
while ( ( currentchar = fgetc( input ) ) != EOF ) {
if ( newline ) {
linecount++;
lineindex = 0;
linesize = 128;
lines = realloc( lines, linecount * sizeof * lines );
lines[linecount - 1] = malloc( linesize );
newline = 0;
}
if ( lineindex == linesize ) {
linesize *= 3;
lines[linecount - 1] = realloc( lines[linecount - 1], linesize );
}
if ( currentchar == '\n' ) {
newline = 1;
currentchar = '\0';
}
lines[linecount - 1][lineindex++] = currentchar;
}
if ( !newline ) {
if ( lineindex == linesize )
lines[linecount - 1] = realloc( lines[linecount - 1], linesize + 1 );
lines[linecount - 1][lineindex] = '\0';
}
int * linestoskip = calloc( linecount, sizeof * linestoskip );
for ( int i = 0; i < linecount; i++ ) {
if ( linestoskip[i] )
continue;
int unique = 1;
for ( int j = i + 1; j < linecount; j++ ) {
if ( linestoskip[j] )
continue;
if ( strcmp( lines[i], lines[j] ) == 0 ) {
unique = 0;
settozero( lines[j] );
linestoskip[j] = 1;
}
}
if ( !unique )
settozero( lines[i] );
}
free( linestoskip );
fseek( input, 0L, SEEK_SET );
for ( int i = 0; i < linecount; i++ ) {
for ( int j = 0; lines[i][j] != '\0'; j++ ) {
fputc( lines[i][j], input );
}
if ( i != linecount - 1 || newline )
fputc( '\n', input );
free( lines[i] );
}
free( lines );
putchar( 10 );
return 0;
}