#include <stdlib.h> // to use realloc
#include <math.h> // to use NAN
#include <stdio.h> // to use printf

double* getpoint(double* points, unsigned dim, unsigned id){
  double* out = malloc(dim * sizeof(double));
  for(unsigned i=0; i < dim; i++){
    out[i] = points[id*dim+i];
  }
  return out;
}

/* dot product of two vectors */
double dotproduct(double* p1, double* p2, unsigned dim){
  double out = 0;
  for(unsigned i=0; i < dim; i++){
    out += p1[i] * p2[i];
  }
  return out;
}

/* middle of segment [p1,p2] */
double* middle(double* p1, double* p2, unsigned dim){
  double* out = malloc(dim * sizeof(double));
  for(unsigned i=0; i<dim; i++){
    out[i] = (p1[i] + p2[i])/2;
  }
  return out;
}

/* vector of NANs */
double* nanvector(int dim){
  double* out = malloc(dim * sizeof(double));
  for(unsigned i=0; i < dim; i++){
    out[i] = NAN;
  }
  return out;
}

// to use the qsort function
int cmpfunc (const void * a, const void * b) {
   return ( *(int*)a - *(int*)b );
}
int cmpfuncdbl (const void * a, const void * b) {
   return ( *(double*)a - *(double*)b > 0 ? 1 : -1);
}
void qsortu(unsigned* vector, unsigned length){
  qsort(vector, length, sizeof(unsigned), cmpfunc);
}


double square(double x){
  return x*x;
}

/* append to a vector of unsigned */
void appendu(unsigned x, unsigned** array, unsigned length, unsigned* flag){
  *flag = 1;
  for(unsigned i=0; i<length; i++){
    if(x==*(*array + i)){
      *flag = 0;
      break;
    }
  }
  if(*flag==1){
    *array = realloc(*array, (length+1)*sizeof(unsigned));
    if(*array == NULL){
      printf("realloc failure - exiting");
      exit(1);
    }
    *(*array + length) = x;
  }
}

/* make a vector of zeros */
unsigned* uzeros(unsigned length){
  unsigned* out = malloc(length * sizeof(unsigned));
  for(unsigned i=0; i < length; i++){
    out[i] = 0;
  }
  return out;
}

/* squared distance between two points */
double squaredDistance(double* p1, double* p2, unsigned dim){
  double out = 0;
  for(unsigned i=0; i < dim; i++){
    out += square(p1[i] - p2[i]);
  }
  return out;
}