city.c

This program can caculate the distance of two city

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#define MAX 1000
#define BUFF 5
typedef struct point_struct {
        int x;
        int y;
        
}point;

typedef struct city_struct{
        point location;
        char *name;
        struct city_struct *next; 
}city, *linkcity;


void getpoint(linkcity L){
    int flag1=1;
    int flag2;
    char yn[BUFF];
    char name[MAX];
    linkcity headptr;           /* moving head point */
    headptr = (linkcity)malloc(sizeof(city));    
    headptr->next=L->next;                   /* get the head point */
    while (flag1){                            /* get the city's location */
        flag2=0;
        printf("want to get the city's location please input its name :");
        scanf("%s",name); 
        while (headptr->next!=NULL){                
         if (strcmp(headptr->next->name,name)==0){             
             printf("your city is at (%d,%d) :)\n", headptr->next->location.x, headptr->next->location.y);
             flag2=1;
             }
            headptr->next=headptr->next->next;
         }
         if (flag2==0)       
         printf("Sorry cannot find it, because you city isn't in the list.\n");
         printf("Do you want to contitue [yes/no]:");        
         scanf("%s",yn);
         if(strcmp(yn,"yes")==0)
             headptr->next=L->next;
         else
             flag1=0;                        
     }
}

linkcity Creatfromhead(){
  char name[MAX];
  city *newcity;
  int n=0; 
  int flag=1;
  linkcity L;               /* head point*/
  L = (linkcity)malloc(sizeof(city));   
  L->next=NULL; 

   while(flag){                               /* add a new note to the list with head point */
     printf("Input the city's name :");
     scanf("%s",name);
     if (strcmp(name,"out")==0)
     flag=0;
     else {
     newcity = (city *) malloc( sizeof(city)+strlen(name)+1);
     newcity->name = (char *)newcity + sizeof(city);
     strcpy(newcity->name,name);
     printf("city's x : ");
     scanf("%d",&newcity->location.x);
     printf("city's y : ");
     scanf("%d",&newcity->location.y);
     printf("%s at (%d,%d)\n",newcity->name,newcity->location.x,newcity->location.y);   
     n++; 
     newcity->next=L->next;
     L->next=newcity;              
         }   
    }
    printf("you have inputed %d city \n",n);
 return L;
}

void findlesscity(linkcity L, point P, double D){               /*find city that it's distance with P is less than S.*/
    linkcity headptr;                                          /* moving head point */
    headptr = (linkcity)malloc(sizeof(city)); 
    headptr->next=L->next;
    while (headptr->next != NULL){
        if(sqrt(1.0*(pow(headptr->next->location.x-P.x , 2 )+pow(headptr->next->location.y-P.y , 2 ))) <= D )
        printf("%s\n",headptr->next->name);
        headptr->next=headptr->next->next;
    }
}

int main ()
{ 
   linkcity L;
   point P;
   double D;
   L=Creatfromhead();
   
   getpoint( L);

   printf("city's x : ");
   scanf("%d",&P.x);
   printf("city's y : ");
   scanf("%d",&P.y);
   printf("input S : ");
   scanf("%lf",&D); 
   findlesscity(L,P,D);                                    
 
}