C++ calculate distance between structure of inputed and saved points and the origin, print out list according on distance -

in task simplified version of obstacles shall modeled points detected imaginary sensor system placed in origin of 2 dimensional local cartesian coordinate system. arbitrary many of such obstacles /points in front of vehicle shall possible store in list. list shall sorted euclidian distance origin (see examples below). (hint: write function calculate euclidian distance d of 2 obstacles/points p1 , p2 coordinates (x1,y1) , (x2,y2) formula: d=√(x1−x2)2+(y1−y2)2 identify them each obstacle/point shall store string ("a", "b", ... in example above), distance , coordinates (xi,yi). (hint: give type definition structure these 4 data components/variables of structure.) in loop in function main arbitrary many of such obstacles/points shall possible inputted , stored in list. afterwards sorted distance list shall outputted. beside string, distance , coordinates in each output string of nearest obstacle/point shall computed , outputted additionaly (see example below). (hint: write further function list of obstacles/points first , 1 obstacle/point second parameter calculating neareast other obstacle/point , returning pointer. take care obstacle/point not return , output distance 0 itself, , @ least 2 obstacles/points need exist; otherwise null pointer nullptr shall returned.)

i able create structure function, distance function , list, unfortunately i'm not able sort , use function distance calculate actual distances.

hope can me!

#include<iostream> #include<cmath>  using namespace std;  double distancecalculate(double x1, double x2, double y1, double y2) {     double x = x1-x2;     double y = y1-y2;     double dist;     dist = pow(x, 2) + pow(y , 2);     dist = sqrt(dist);     return dist; }  struct point {     char name [1];     double x, y, origin_distance ;     struct point *next; };  int main(void) {     int choice;     struct point *head = nullptr, *newelement, *p ;         {         cout << "0 end"<< endl;         cout <<"1 input point"<< endl;         cout <<"2 print list of points" << endl;         cin >> choice;         switch(choice)          {         case 1:             newelement = new point;             if (newelement == nullptr)                 cerr << "not enough free memory " << endl;             else             {                 cout<< "please enter point's name: ";                 cin>> newelement ->name;                 cout << "please input value x:";                 cin >> newelement->x;                 cout <<"please input value y:";                 cin >> newelement->y;                 newelement ->next = head;                 head = newelement;             }             break;         case 2:             cout<< "print list of points"<< endl;             cout<< "name.\t x.\t y.\t" << endl;             p=head;             while (p!= nullptr)             {                 cout<< p->name<<"\t"<< p->x<<"\t" << p->y << "\t" << endl;                 p=p->next;             }             break;           }     } while (choice !=0);     return 0; } 

the first thing notice you're mixing definitions of point , of (linked)list node. more typical implementation see defining 2 types - 1 point , list node. perhaps like:

typedef struct point {  double x, y; }; typedef struct listnode {   point data;   listnode *next; }; 

however, reading question - doesn't appear defining type capable of representing list part of task. such, may leave std library. i've done that, using std::vector container hold list of points.

not need concern defining datatype hold 2d point, easy sorting free. define function return true or false, depending on whether 1 element should come before next, or not.

there looks nothing wrong distance function, though i'd avoid using pow function when squaring - i'd use x*x + y*y

another advantage of using std::vector type, can access elements contains using standard array notation. in mind, display nearest , furthest points origin, can sort list display pointlist[0] , pointlist[numelements-1].

here's rough implementation:

#include <cmath> #include <cstdlib> #include <cstdio> #include <vector> #include <algorithm>  typedef struct vec2_t {     double x;     double y; } *pvec2;  typedef std::vector<vec2_t> vecvectors; typedef vecvectors::iterator vecvectorsiter;  double distbetween(vec2_t &p1, vec2_t &p2) {     double dx = p1.x - p2.x, dy = p1.y - p2.y;     return sqrt( dx*dx + dy*dy); } bool orderpointasc(vec2_t &p1, vec2_t &p2) {     vec2_t origin = {0.0,0.0};     return (distbetween(origin,p1) < distbetween(origin,p2)); }  int main() {     vecvectors pointlist;     vec2_t origin = {0.0, 0.0};     int i, n=10;      vec2_t tmp;     (i=0; i<n; i++)     {         tmp.x = 100 * (rand() % 0xffff) / 65535.0;         tmp.y = 100 * (rand() % 0xffff) / 65535.0;         pointlist.push_back(tmp);         printf("%d. - <%5.02f, %5.02f> - dist origin: %0.02f\n", i, tmp.x, tmp.y, distbetween(origin, tmp));     }     printf("sorting...\n");     std::sort(pointlist.begin(), pointlist.end(), orderpointasc);     (vecvectorsiter iter = pointlist.begin(); iter!=pointlist.end(); iter++)     {         printf("<%5.02f, %5.02f> - %5.02f\n", (*iter).x, (*iter).y, distbetween(origin, (*iter)) );     }      return 0; } 

sample output

0. - < 0.06, 28.18> - dist origin: 28.18 1. - < 9.67, 40.44> - dist origin: 41.58 2. - <29.25, 23.99> - dist origin: 37.83 3. - <17.51, 44.80> - dist origin: 48.10 4. - <41.14, 37.33> - dist origin: 55.55 5. - < 8.71, 42.95> - dist origin: 43.82 6. - <35.52, 25.68> - dist origin: 43.83 7. - <15.20,  0.75> - dist origin: 15.22 8. - < 4.57, 18.22> - dist origin: 18.79 9. - < 7.37,  8.29> - dist origin: 11.09 sorting... < 7.37,  8.29> - 11.09 <15.20,  0.75> - 15.22 < 4.57, 18.22> - 18.79 < 0.06, 28.18> - 28.18 <29.25, 23.99> - 37.83 < 9.67, 40.44> - 41.58 < 8.71, 42.95> - 43.82 <35.52, 25.68> - 43.83 <17.51, 44.80> - 48.10 <41.14, 37.33> - 55.55