What is wrong with my code?? perimeter.c - c

Question

Okay, this is not working!
What is wrong with it.
Can somebody point it out to me. I've stared at it for hours.
I have seeked help earlier and he come up with struct but im not really getting it and it doesnt work so.
It's not getting the right calculation. I'm thinking that there might be something wrong with reading the files.
/*
read binary file and calculate parameter of polygon
*/
typedef int16_t points[2];
int main(int argc, char* argv[]) {
FILE* fp = fopen(argv[1], "rb");
// int points[1000];
//long numbytesread=0;
int16_t num_of_coors=0;
//open the files
if( fp == NULL ) {
printf("Could not open.\n");
return -1; // -1 indicates error
}
//read file
fread(&num_of_coors, sizeof(int16_t), 2, fp);
points*points=malloc(sizeof(points)*num_of_coors);
fread(points, sizeof(points), num_of_coors, fp);
//read the array and seperate x coordinates and y coordinates
//calculate using formula (x1-x2)^2+(y1-y2)^2
//need 2 points, 4 coordinates at any single time. read a pair at a time
double sum=0;
int i=0;
//int coors=points[0]*2+1 ;
for(i=1;i<=num_of_coors;i++){
sum+=sqrt(pow((points[i]-points[i+2]),2) + pow((points[i+1]-points[i+3]),2));
}
sum+=sqrt(pow((points[1]-points[num_of_coors-2]),2) + pow((points[2]-points[num_of_coors-1]),2));
printf("The perimeter is %.2lf\n", sum);
fclose(fp);
free(points);
}

Answer 1

I guess the binary format of your file is:
int16_t <num of points>
int16_t <Xcoord> int16_t <Ycoord>
....
First, it is bad way to use same name for type name and for variable name.
Second, you work with 'points' type is incorrect.
The correct code should looks like:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
/*
read binary file and calculate parameter of polygon
*/
typedef int16_t points[2];
int main(int argc, char* argv[]) {
FILE* fp = fopen(argv[1], "rb");
// int points[1000];
//long numbytesread=0;
int16_t num_of_coors=0;
//open the files
if( fp == NULL ) {
printf("Could not open.\n");
return -1; // -1 indicates error
}
//read file
fread(&num_of_coors, sizeof(int16_t), 1, fp);
points* p=malloc(sizeof(points)*num_of_coors);
fread(p, sizeof(points), num_of_coors, fp);
//read the array and seperate x coordinates and y coordinates
//calculate using formula (x1-x2)^2+(y1-y2)^2
//need 2 points, 4 coordinates at any single time. read a pair at a time
double sum=0;
int i=0;
//int coors=points[0]*2+1 ;
for(i=1;i<num_of_coors;i++) {
sum+=sqrt(pow(p[i-1][0]-p[i][0],2)+pow(p[i-1][1]-p[i][1],2));
}
sum+=sqrt(pow(p[0][0]-p[num_of_coors-1][0],2)+pow(p[0][1]-p[num_of_coors-1][1],2));
printf("The perimeter is %.2lf\n", sum);
fclose(fp);
free(p);
return 0;
}