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  1. #include <stdio.h>
  2. #include <math.h>
  3.  
  4. double dot_product (double *a, double *b, size_t n) {
  5.   double acc=0;
  6.   for (size_t i=0; i < n; ++i)
  7.     acc += a[i]*b[i];
  8.   return acc;
  9. }
  10.  
  11. int is_ortho (double *m, size_t n) {
  12.   for (size_t i=0; i < n; ++i) {
  13.     for (size_t j=i; j < n; ++j) {
  14.        double p=dot_product (m+i*n, m+j*n, n);
  15.        if (i==j) { if (fabs(p-1) > 1e-6) return 0; }
  16.        else      { if (       p  > 1e-6) return 0; }
  17.     }
  18.   }
  19.   return 1;
  20. }
  21.  
  22. int main(void) {
  23. 	double m1[] = { 0.96, -0.28, 0.28, 0.96 };
  24. 	double m2[] = { 1, 0, 0, -1 };
  25. 	double m3[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
  26. 	double m4[] = { 1 };
  27. 	printf ("%d", is_ortho(m1, 2));
  28. 	printf ("%d", is_ortho(m2, 2));
  29. 	printf ("%d", is_ortho(m3, 3));
  30. 	printf ("%d", is_ortho(m4, 1));
  31. 	return 0;
  32. }
  33.  
Success #stdin #stdout 0s 2248KB
comments (?)
stdin 
Standard input is empty
stdout 
1101
https://ideone.com/v7qDMW
language:
C99 (gcc 8.3)
created:
12 years ago
visibility:
public

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