Checking for point in polygon

IsPointInPolygon.swift

func IsPointInPolygon(p: CLLocationCoordinate2D, polygon: [CLLocationCoordinate2D]) -> Bool {
        
        var minX: Double = polygon[0].latitude
        var maxX: Double = polygon[0].latitude
        var minY: Double = polygon[0].longitude
        var maxY: Double = polygon[0].longitude
        
        for i in 0...polygon.count{
            let q : CLLocationCoordinate2D = polygon[i];
            minX = min(q.latitude, minX)
            maxX = max(q.latitude, maxX)
            minY = min(q.longitude, minY)
            maxY = max(q.longitude, maxY)
        }
        
        if ( p.latitude < minX || p.latitude > maxX || p.longitude < minY || p.longitude > maxY )
        {
            return false
        }
        
        var inside : Bool = false;
        
        
        for ( int i = 0, j = polygon.Length - 1 ; i < polygon.Length ; j = i++ )
        {
            if ( ( polygon[i].longitude > p.longitude ) != ( polygon[j].longitude > p.longitude ) &&
                p.X < ( polygon[j].latitude - polygon[i].latitude ) * ( p.longitude - polygon[i].longitude ) / ( polygon[j].longitude - polygon[i].longitude ) + polygon[i].latitude )
            {
                inside = !inside;
            }
        }
        
        return inside;
    }