Read 2 files in C to calculate Manhattan Distance - c

Question

I need some help just starting off my code for this program. This is my first time reading a file in c and I have been stuck starting it off. Essentially, I need to read in two files to calculate Manhattan Distance and output the ID for each file and the closest distance. The files look something like this:
3,2
0, 3.4, 4.3
1, 4.5, 6.1
2, 7.2, 3.9
3,2
0, 5.9, 6.7
1, 8.5, 1.2
2, 9.8, 4.9
My current code only outputs the table and I am trying to find a way to use columns as a way to calculate Manhattan distance. The 3,2 signifies the rows and columns and the 0,1,2 are the IDs. Here is the current code I have found online and modified a bit that I thought may be useful.
#include <stdio.h>
#include <string.h>
int main()
{
FILE* testFile = fopen("Test.txt", "r");
if (!testFile)
printf("Can't open file\n");
else {
char buffer[1024];
int row = 0;
int column = 0;
while (fgets(buffer, 1024, testFile)) {
column = 0;
row++;
if (row == 1)
continue;
// Splitting the data
char* value = strtok(buffer, ", ");
while (value) {
// Column 1
if (column == 0) {
printf("TestID:");
}
// Column 2
if (column == 1) {
printf("\tx1: ");
}
// Column 3
if (column == 2) {
printf("\ty1: ");
}
printf("%s", value);
value = strtok(NULL, ", ");
column++;
}
printf("\n");
}
// Close the file
fclose(testFile);
}
return 0;
}

Answer 1

Here's a basic example demonstrating one method of parsing your input files with strtod and strtoul:
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct mat {
int rows;
int columns;
double *data;
};
void
show(const struct mat *A)
{
double *d = A->data;
for( int i = 0; i < A->rows; i += 1 ){
for( int j = 0; j < A->columns; j += 1 ){
printf("%f\t", *d++);
}
putchar('\n');
}
}
/*
* Return nonzero if the first non-whitespace
* character after *e is not v. Terminate search
* at a newline.
*/
int
expect_next(char **e, const char v)
{
char *end = *e;
while( isspace(*end) && *end != '\n' ){
end += 1;
}
*e = end + 1;
return *end != v;
}
int
get_data(struct mat *A, const char *path)
{
unsigned line = 1;
FILE* testFile = fopen(path, "r");
if( testFile == NULL ){
perror(path);
return 0;
}
char buffer[1024];
char *end = buffer;
if( fgets(buffer, sizeof buffer, testFile) == NULL ){
if( ferror(testFile) ){
perror(path);
} else {
goto bad_input;
}
return 0;
}
A->rows = strtoul(buffer, &end, 10);
if( expect_next(&end, ',') ){
goto bad_input;
}
A->columns = strtoul(end, &end, 10);
if( expect_next(&end, '\n') ){
goto bad_input;
}
A->data = malloc(A->rows * A->columns * sizeof *A->data);
if( A->data == NULL ){
perror("malloc");
return 0;
}
double *val = A->data;
unsigned row = 0;
while( NULL != fgets(buffer, sizeof buffer, testFile) ){
line += 1;
unsigned v = strtoul(buffer, &end, 10);
if( v != row ){
goto bad_input;
}
if( expect_next(&end, ',') ){
goto bad_input;
}
unsigned col = 0;
while( col < A->columns && *end ){
*val++ = strtod(end, &end);
if( expect_next(&end, ++col == A->columns ? '\n' : ',') ){
goto bad_input;
}
}
if( col != A->columns ){
goto bad_input;
}
row += 1;
}
if( row != A->rows ){
goto bad_input;
}
if( fclose(testFile) ){
perror(path);
}
return 1;
bad_input:
fprintf(stderr, "%s: Invalid input at line %u, column %u\n", path,
line, (unsigned)(end - buffer));
return 0;
}
int
main(int argc, char ** argv)
{
char *args[] = { NULL, "/dev/stdin", NULL };
if( argc < 2 ){
argv = args;
}
for( argv += 1; *argv; argv += 1 ){
struct mat A;
if( get_data(&A, *argv) ){
show(&A);
}
}
}