Hi guys I'm trying to get this program to sort my array in the second option and i think i have the bubble sort written correctly but it doesn't do anything. Any ideas

//This program takes 20 inputs from the user, and gives the choice to show sorted data,

//sort the data into descending order, display the sorted data, and display the address of the first element.

Code:

#include <iostream>
using namespace std;
#include <iomanip>
#include <algorithm>
int main()
{
int i,num[20],n,j,choice,tmp;
cout<< "Please enter 20 integers";
for (i=0; i<20; i++)
{
cout<<"\nEnter next value:";
cin>>num[i];
}
cout<<"\n1.Display original data.\n";
cout<<"2.Sort the data into descending order\n";
cout<<"3.Display the sorted data (Only if you've already sorted)\n";
cout<<"4.Get the address of the first element of array.\n\n";
cin>>choice;
if (choice==1){
for (i=0; i<20; i++){
cout<<"\n"<<num[i]<<endl;
}
if (choice==2){
for (i=0; i<n-1; i++) {
for (j=0; j<n-1-i; j++)
if (num[j+1] < num[j]) { /* compare the two neighbors */
tmp = num[j]; /* swap a[j] and a[j+1] */
num[j] = num[j+1];
num[j+1] = tmp;
cout<<"Here are your numbers:"<<tmp<<endl;
}
}
}}}