How to find the nearest marker and calculate the distance to it using Google Maps API?

Question

C++ / C#

There is such a code with an array that contains the coordinates of the marks and the script for adding a mark by clicking on the map / input:

js code itself

var coord = [
    {"id": 1, "coordlat": 47.2200, "coordlng": 39.6170},
    {"id": 2, "coordlat": 47.2882, "coordlng": 39.6643},
    {"id": 3, "coordlat": 47.2190, "coordlng": 39.7162},
    {"id": 4, "coordlat": 47.2502, "coordlng": 39.7930},
    {"id": 5, "coordlat": 47.2503, "coordlng": 39.5639},
    {"id": 6, "coordlat": 47.2612, "coordlng": 39.6854},
    {"id": 7, "coordlat": 47.2830, "coordlng": 39.6253},
    {"id": 8, "coordlat": 47.2799, "coordlng": 39.7486},
    {"id": 9, "coordlat": 47.1972, "coordlng": 39.6569},
];

var delAdress = $('input"]');
var markers = [];
var coords = [];
var map;

function initMap() {
    map = new google.maps.Map(document.getElementById('map'), {
        zoom: 11,
        center: {lat: 47.2381, lng: 39.7002}
    });
    var geocoder = new google.maps.Geocoder();
    for( i = 0; i < coord.length; i++ ) {
        var position = new google.maps.LatLng(coord[i].coordlat, coord[i].coordlng);
        marker = new google.maps.Marker({
            position: position,
            map: map,
        });
        coords.push(marker);
    };
    document.getElementById('btn').addEventListener('click', function() {
        if(delAdress.val()==''){
            return false;
        } else{
            geocodeAddress(geocoder, map);
        }
    });
    map.addListener('click', function(event) {
          addMarker(event.latLng);
    });
};

function addMarker(location){
    setMapOnAll(null);
    markers = [];
    var marker = new google.maps.Marker({
        position: location,
        map: map,
    });
    markers.push(marker);
};

function geocodeAddress(geocoder, resultsMap) {
    
    var address = document.getElementById('suggestions').value;
    
    geocoder.geocode({'address': address}, function(results, status) {
        if (status === 'OK') {
            setMapOnAll(null);
            markers = [];
            resultsMap.setCenter(results[0].geometry.location);
            var marker = new google.maps.Marker({
                map: map,
                position: results[0].geometry.location,
            });
            markers.push(marker);
        } else {
            console.log('Geocode was not successful for the following reason: ' + status);
        }
    });
};

function setMapOnAll(map) {
    for (var i = 0; i < markers.length; i++) {
        markers[i].setMap(map);
    }
}

Duplicate on JSFiddle
And the question is, when adding a marker by the user, find the nearest added marker from the array and calculate the distance to it?

Answer 1

Your edited code:

#include<iostream> 
#include<fstream> 
#include<string>
using namespace std;
struct book
{
  string name;
  unsigned year;
  unsigned circulation;
};
void sort(book* arr, book* array1, const unsigned& N);
unsigned kolvo(book* arr, const unsigned&N);
int main()
{
  unsigned n, N; bool otkr;
  setlocale(LC_ALL, ""); book* arr = NULL;
  cout << "ВЫБЕРИТЕ СПОСОБ ВВОДА. 0 - С КЛАВИАТУРЫ, 1 - ИЗ ФАЙЛА  \n"; cin >> otkr;
  if (!otkr)
  {
    cout << "ВВЕДИТЕ РАЗМЕР МАССИВА:\n";
    cin >> N;
    arr = new book[N];
    for (int i = 0; i < N; i++)
    {
      cout << "ВВЕДИТЕ НАЗВАНИЕ КНИГИ:\n";
      cin >> arr[i].name;
      cout << "ВВЕДИТЕ ТИРАЖ:\n";
      cin >> arr[i].circulation;
      cout << "ВВЕДИТЕ ГОД \n";
      cin >> arr[i].year;
    };
    for (int i = 0; i < N; i++)
    {
      cout << arr[i].name << "  " << arr[i].circulation << "  " << arr[i].year << endl;
    };
  }
  else
  {
    ifstream knigi("TextFile1.txt");
    knigi >> N;
    arr = new book[N];
    for (int i = 0; i < N; i++)
    {
      knigi >> arr[i].name >> arr[i].circulation >> arr[i].year;
    }
  };
  if ((n = kolvo(arr, N)) == 0)
  {
    cout << "no matches";
    return 0;
  }
  book* array1 = new book[n]; cout<<endl;
  sort(arr, array1, N);
  for (int i = 0; i < n; i++)
  {
    cout << "КНИГИ НАПЕЧАТАННЫЕ С 2000 ПО 2010 :" << arr[i].name << "  " << arr[i].circulation << endl;
  }
  return 0;
}

void sort(book* arr, book* array1, const unsigned&N)
{
  unsigned counter = 0;
  for (auto i = 0; i < N; i++)
  {
    if ((arr[i].year > 1999) && (arr[i].year < 2011))
    {
      array1[counter].name = arr[i].name;
      array1[counter++].circulation = arr[i].circulation;
    }
  }
}

unsigned kolvo(book* arr, const unsigned &N)
{
  unsigned number = 0;
  for (int i = 0; i < N; i++)
  {
    if (arr[i].year > 1999 && arr[i].year < 2011)
    {
      number++;
    }
    return(number);
  }
}

Answer 2

https://stackoverflow.com/questions/4057665/google...
But that's all cool as long as you have a hundred other points. Wisely, you need to use spatial indexes and specially sharpened algorithms https://github.com/mourner/rbush-knn