add FindLeader function

class_model/include/class_model/DroneStatus.h

@@ -4,7 +4,7 @@ typedef struct DroneStatus
 {
     /* data */
     global_location init_location;
-    int plane;
+    int plane,ID;
     std::string leader;
     std::string DroneName;
 } DroneStatus;

class_model/include/class_model/FindLeader.h

@@ -0,0 +1,30 @@
+#include "class_model/gps_location.h"
+#include "class_model/DroneStatus.h"
+#include <iterator> 
+
+bool is_leader(global_location data[], size_t index){
+    
+    float d[index];
+    int check_ID,leader_ID;
+
+    for(int i=1 ; i<index ; i++){
+
+        d[data[i].ID] = sqrt( pow((data[0].lat - data[i].lat),2) + pow((data[0].lon - data[i].lon),2) );
+
+        // std::cout << i<<"," <<d[data[i].ID] <<std::endl;
+    }
+
+    std::vector<float> _d(d+1,d+index-1); 
+    
+    check_ID = std::distance(_d.begin(),std::min_element(_d.begin(),_d.end()));     //get minimum value's index
+    leader_ID = check_ID + 1;
+    
+    std::cout <<"Drone " << leader_ID << " is leader " << std::endl;
+    
+    if (data[1].ID == leader_ID){
+        return 1;
+    }else{
+        return 0;
+    }
+    
+}