finding index of a number

[raijin011321]

C++,
How do i make choice "C" to find the index of the value entered by the user? Here are my codes.

#include <iostream>
using namespace std;

int main()
{
   int arr[20];
   char select;

   cout << "Enter 20 nonnegative integers: ";
   cout << endl;
   for(int i=0; i<20; i++){
    cout << "Element for " << i << ": ";
    cin >> arr[i];
   }
   cout << endl;
   cout << "A. Display\n";
   cout << "B. Sort\n";
   cout << "C. Search\n";
   cout << endl;

   cout << "Please select a choice above: ";
   cin >> select;
   cout << endl;

   switch(select)
   {
       case 'a': cout << "A. You chose to Display";
                cout << endl;
                break;

       case 'b': cout << "B. You chose to Sort";
                cout << endl;
                break;

       case 'c': cout << "C. You chose to Search";
                cout << endl;
                break;
   }

   if(select == 'a')
   {
       cout << "The elements you entered are: ";
       for(int i=0; i<20; i++){
        cout << arr[i] << " ";
       }
   }
   else if(select=='b'){
    for(int i=0; i<20; i++){
        for(int j=0; j<20; j++){
            if(arr[j] > arr[j+1]){
                int temp = arr[j];
                arr[j] = arr[j+1];
                arr[j+1] = temp;
            }
        }
    }
    cout << "Sorted Array elements: ";
    for(int i=0; i<20; i++){
        cout << arr[i] << " ";
    }
    cout << endl;
   }
   else if (select=='c'){
        cout << "Enter a number to be searched: ";

   }

    return 0;
}

[seeplus]

There are various issues with the code. Why use a switch() and then have if statements? There's also an issue with the bubble sort. Note that c++ has a std::swap() function. There is also a std::sort() function that could be used unless you have to code your own

https://cplusplus.com/reference/algorithm/sort/.

Perhaps something like this:

#include <iostream>
#include <utility>
using namespace std;

int main() {
	int arr[20] {};

	cout << "Enter 20 non-negative integers:\n";

	for (int i = 0; i < 20; ) {
		cout << "Element for " << i << ": ";
		cin >> arr[i];

		if (arr[i] < 0)
			std::cout << "Number must not be negative\n";
		else
			++i;
	}

	for (char select {}; select != 'd'; ) {
		cout << "\na. Display\n";
		cout << "b. Sort\n";
		cout << "c. Search\n";
		cout << "d. Quit\n";

		cout << "\nPlease select a choice above: ";
		cin >> select;

		switch (select) {
			case 'a':
				cout << "\na. You chose to Display\n";
				cout << "The elements are:\n";

				for (int i = 0; i < 20; i++)
					cout << arr[i] << " ";

				cout << '\n';
				break;

			case 'b':
				cout << "b. You chose to Sort\n";

				for (int i = 0; i < 19; ++i)
					for (int j = 0; j < 19 - i; ++j)
						if (arr[j] > arr[j + 1])
							swap(arr[j], arr[j + 1]);

				break;

			case 'c':
				{
					int n {};

					cout << "C. You chose to Search";
					cout << "\nEnter a number to be searched: ";
					cin >> n;

					bool fnd {};

					for (int i = 0; i < 20; ++i)
						if (arr[i] == n) {
							std::cout << "Number found at index " << i << '\n';
							fnd = true;
							break;
						}

					if (!fnd)
						std::cout << "Number not found!\n";
				}
				break;

			case 'd':
				break;

			default:
				cout << "Invalid option\n";
				break;
		}
	}
}

Also note that where a size of an array is used, this is usually coded as a const variable at the beginning of the program so if the size needs to be changed, there is only one place to change.