can you help me figure this out. Ok for option (l) which means show all the plan

Question

can you help me figure this out. Ok for option (l) which means show all the planets in the database I need a way to check if the array is empty or not to output that there are no planets in the database, can you please help me , also Im not suppose to use include <string>

what else can I use to save the complete word ex terrestial

#include<iostream>
#include<string>

using namespace std;

int main()
{
   //variable declarations.
   int num = 0;
   int plannum[10];
   int i;
   for (i = 0; i < 10; i++)
   {
       plannum[i] = -1;
   }
   float diameter[10];
   float temp[10];
   float distance[10];
   string nature[10];
   char choice;

   //Menu driven program !
   cout << "Please make your selection: (a)dd a planet, (s)elect a planet, (l)ist all planets, (q)uit: ";
   cin >> choice;
   while (choice != 'q')
   {
       //This choice its to add a planet!
       if (choice == 'a')
       {
           plannum[num] = num;

           cout << "Please enter the diameter of planet number " << num << ": ";
           cin >> diameter[num];
           cout << "Please enter the average temperature of planet number " << num << ": ";
           cin >> temp[num];
           cout << "Please enter the planets distance from its star in millions of miles " << num << ": ";
           cin >> distance[num];
           cout << "Please enter the type of the planet " << num << ": ";
           cin >> nature[num];

           num++;// adds the num of the planet by 1!

           cout << "Please make your selection: (a)dd a planet, (s)elect a planet, (l)ist all planets, (q)uit: ";
           cin >> choice;

       }
       //Search a planet's characteristics by planet number!
       else if (choice == 's')
       {
           cout << "Specify the planet number: ";
           cin >> num;

           //If the planet number dosnt match then there are no planets in the database!
           if (plannum[num] == -1){
               cout << "That planet is not currently in the database." << endl;
               cout << "Please make your selection: (a)dd a planet, (s)elect a planet, (l)ist all planets, (q)uit: ";
               cin >> choice;

           }
           //Otherwise cout all the characteristics inputed by the user!
           else
           {
               cout << "Data for Planet" << num << ": " << endl;
               cout << " Diameter: " << diameter[num] << "miles." << endl;
               cout << " Distance for its star: " << temp[num] << " million miles." << endl;
               cout << " Average Temperature: " << distance[num] << " degrees F." << endl;
               cout << " Type: " << nature[num] << endl;

               cout << "Please make your selection: (a)dd a planet, (s)elect a planet, (l)ist all planets, (q)uit: ";
               cin >> choice;

           }

       }
       //This is cout all the planet's charcteristics with their corresponding planet number in the database!.
       else if (choice == 'l')
       {

           //In case there are no planets in the database yet! THIS IS NOT WORKING I NEED TO FIND OUT IF THE ARRAY IS EMPTY
           if (plannum[i] != 0)
           {
               cout << "There are no planets in the database!" << endl;
               cout << "Please make your selection: (a)dd a planet, (s)elect a planet, (l)ist all planets, (q)uit: ";
               cin >> choice;

           }
           //If there are planets in the database then show them!
           else
           {

               cout << "Planets in the database: " << endl;

               for (i = 0; i < 10; i++){
                   cout << "Planet " << i << ": ";

                   cout << "Diameter: " << diameter[num] << " miles. ";

                   cout << "Distance for its star:" << distance[num] << " million miles. ";

                   cout << "Average Temperature: 65" << temp[num] << " degrees F. ";
                   cout << " Type: " << nature[num] << endl;
                   //This if statement its to output if the planet its habitable or not!
                   if (nature[num] == "terrestrial")
                       cout << " Habitable: possibly. ";
                   else
                       cout << " Habitable: impossible. ";
               }
               cout << "Please make your selection: (a)dd a planet, (s)elect a planet, (l)ist all planets, (q)uit: ";
               cin >> choice;
           }
       }
   }
}

Explanation / Answer

if you have noticed num is the counter represents how many planet in our database, if num = 0 means no planet in the database.


else if (choice == 'l'){
//In case there are no planets in the database yet! THIS IS NOT WORKING I NEED TO FIND OUT IF THE ARRAY IS EMPTY
if (num == 0){
cout << "There are no planets in the database!" << endl;
cout << "Please make your selection: (a)dd a planet, (s)elect a planet, (l)ist all planets, (q)uit: ";
cin >> choice;
}
//If there are planets in the database then show them!
else{
cout << "Planets in the database: " << endl;
for (i = 0; i < num; i++){
cout << "Planet " << i << ": ";
cout << "Diameter: " << diameter[num] << " miles. ";
cout << "Distance for its star:" << distance[num] << " million miles. ";
cout << "Average Temperature: 65" << temp[num] << " degrees F. ";
cout << " Type: " << nature[num] << endl;
//This if statement its to output if the planet its habitable or not!
if (nature[num] == "terrestrial")
cout << " Habitable: possibly. ";
else
cout << " Habitable: impossible. ";
}
cout << "Please make your selection: (a)dd a planet, (s)elect a planet, (l)ist all planets, (q)uit: ";
cin >> choice;
}

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