Defibrillators

The aim of this puzzle is to find the closest defibrillators in a list. The main difficulty is that for each defibrillator of the list are given not only coordinates, but also a lot of useless information. That is why this puzzle involves a lot of string manipulation.

C

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <float.h>

// represents a defibrillator
struct defib { char* name; double lon; double lat; };

/* Returns the distance between a point A and a point B 
   given their lat(itude) and lon(gitude)*/
double distance(double longA, double latA, double longB, double latB){
    double x = (longB-longA)*cos((latA+latB)/2);
    double y = latB - latA;
    return (sqrt(x*x+y*y) * 6371.0);
}

// Parses a double in string 'str' using atof, and replacing , by . if needed
double toDouble(char *str) {
    for(char *iter = str; *iter != '\0'; iter++)
        if (*iter == ',')
            *iter = '.';
    return atof(str);
}

// Returns a pointer on next char 'c' in 'str'
char *goToNext(char c, char *str) {
    for(; *str != c; str++);
    return str;
}

/* Reads the line 'str', and stores relevant fields in 'defib'
   pretty awful implementation, but necessary for speed*/
void getDefib(char *str, struct defib *res) {
    str = goToNext(';', str);
    res->name = ++str;
    for (int k = 0; k < 3; k++) {
        str = goToNext(';', str);
        *str = '\0';
        str++;
    }
    char *lon = str;
    str = goToNext(',', str);
    *str = '.';
    str = goToNext(';', str);
    char *lat = ++str;
    str = goToNext(',', str);
    *str = '.';
    res->lon = atof(lon);
    res->lat = atof(lat);
}

int main(int argc, char** argv)
{
    char strLon[50];
    char strLat[50];
    int N;
    scanf("%s\n%s\n%d\n", strLon, strLat, &N);
    double lon = toDouble(strLon);
    double lat = toDouble(strLat);
    
    // simple linear search amongst defibrillators
    double min = DBL_MAX;
    char output[100];
    double d;
    char line[256];
    struct defib res;

    for (int i = 0; i < N; i++) {
        getDefib(fgets(line, 256, stdin), &res);
        d = distance(lon, lat, res.lon, res.lat);
        if (d < min) {
            min = d;
            strcpy(output, res.name);
        }
    }
    printf("%s", output);
    return EXIT_SUCCESS;
}

Java

import java.util.*;
import java.math.*;

class Solution {
    /** Returns the distance between a point A and a point B
     * @param longA longitude of point A
     * @param latA latitude of point A
     * @param longB longitude of point B
     * @param latB latitude of point B
     * @return distance between A and B
     */
    private static double distance(double longA, double latA, double longB, double latB){
        double x = (longB-longA)*Math.cos((latA+latB)/2);
        double y = latB - latA;
        return Math.sqrt(Math.pow(x,2) + Math.pow(y,2)) * 6371;
    }

    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        
        /* as the latitude and the longitude are given with , instead of .
           it isn't possible to use nextFloat()*/
        Double lon = new Double(in.next().replace(',', '.'));
        Double lat = new Double(in.next().replace(',', '.'));
        int N = in.nextInt();
        in.nextLine();

        // simple min search amongst defibrillators
        double min = Double.POSITIVE_INFINITY;
        String res = "";
        Double d;
        for (int i = 0; i < N; i++) {
            String[] defib = in.nextLine().replace(',', '.').split(";");
            d = distance(lon, lat, new Double(defib[4]), new Double(defib[5]));
            if (d < min) {
                min = d;
                res = defib[1];
            }
        }
        System.out.println(res);
    }
}

Python 3

import math

def distance (longA, latA, longB, latB):
    ''' return the distance between point A and point B 
    given their latitude and longitude '''
    x = (longB-longA)*math.cos((latA+latB)/2)
    y = latB-latA
    return 6371 * math.sqrt(x*x+y*y)

lon, lat, N = float(input().replace(",", ".")), float(input().replace(",", ".")), int(input())
# linear search amongst defibrillators
min, res = None, None
for i in range(N):
    defib = input().replace(",", ".").split(";")
    d = distance(lon, lat, float(defib[4]), float(defib[5]))
    if (min == None) or (d < min):
        min, res = d, defib[1]
print(res)