Informatics3-2024/Solutions2

Solutions

Only the solutions we discussed on the practical will be here. All the other tasks are perfect to practice for the written exam.

Distance

#include<stdio.h>
#include<math.h> // need this for sqrt
 
struct point2 { // our struct type
  float x;
  float y;
};
 
// we need 2 points to calculate their distance
// root of ((x1-x2)^2 + (y1-y2)^2)
float distance(struct point2 a, struct point2 b) {
  // don't need to separate the calculation into smaller parts, you can do it in one line as well
  float x_part = a.x - b.x; // x1 - x2
  float y_part = a.y - b.y; // y1 - y2
  float sum = x_part * x_part + y_part * y_part;
  return sqrt(sum);
}
 
// testing here
int main(void) {
  struct point2 p1;
  struct point2 p2;
  p1.x = 1; p1.y = 1;
  p2.x = 2; p2.y = 2;
  printf("%f\n", distance(p1, p2));
  return 0;
}

Min-max

#include<stdio.h>
 
void swap(int *min, int *max) { // 2 pointer parameters
  if (*min > *max) { // do we need to swap?
    int temp;  // temporary variable
    temp = *min;
    *min = *max;
    *max = temp;
  }
}
 
// just testing here
int main(void) {
  int a = 5;
  int b = 7;
  int c = 9;
  printf("%d, %d, %d\n", a, b, c);
  swap(&a, &b);
  swap(&c, &a);
  printf("%d, %d, %d\n", a, b, c);
  return 0;
}

Sort

#include<stdio.h>
 
void swap(int *min, int *max) { // previous task
  if (*min > *max) {
    int temp;
    temp = *min;
    *min = *max;
    *max = temp;
  }
}
 
void sort(int a[], int n) { // bubble sorting an array
  int i, j; // cycle variables
  // two cycles needed
  // check what happens if you remove one of them
  for(j = 0; j < n-1; j++) {
    for(i = 0; i < n-1; i++) {
      swap(&a[i], &a[i+1]); // we swap if needed
      //printf("%d, %d\n", a[i], a[i+1]); //for testing
    }
  }
}
 
int main(void) {
  int a[] = {5, 4, 8, 2}; // creating the test array
  int i; // cycle variable
  for(i = 0; i < 4; i++) {
    printf("%d ", a[i]); // printing the initial array
  }
 
  sort(a, 4); // calling the function we're testing
  printf("\nsorting done\n");
 
  for(i = 0; i < 4; i++) {
    printf("%d ", a[i]); // printing the sorted array
  }
  printf("\n");
  return 0;
}