Reading an array backwards & printing!

[ENhkSL3A]

Hey guys! I'm having a user input a vector and blah blah. Any who, I need to know how to use the member function
vest.reverse();
in order to read the vector backwards. Here is my code so far :)

#include <iostream>

using namespace std;

int main()
{

	cout << "Kaitlin Stevers" << endl;
	cout << "Exercise 9A - Print Array" << endl;
	cout << "October 31, 2016" << endl;
	cout << endl;
	cout << endl;
	int numOfValues;
	cout << "Please enter the number of values you need stored. " << endl;
	cin >> numOfValues;
	int count;

	const int ARRAY_SIZE = 50;
	int val[ARRAY_SIZE]; 
	
	
	for (count = 0; count < numOfValues; count++)
	{
		cout << "Enter an integer value: ";
		cin >> val[count];
	}

		cout << "Here are the values you entered:\n";
		for (count = 0; count < numOfValues; count++)
			cout << " " << val[count];
			cout << endl;
		
		cout << "Here are the values backwords: /n";
		for (count =0; count < numOfValues; count++)
			vect.reverse(val);
		
	return 0;
}

[SakurasouBusters]

#include <iostream>
#include <vector>

using namespace std;

int main()
{
	int i;
	cout << "Kaitlin Stevers (kns2872) on Cplusplus forum" << endl;
	cout << "Exercise 9A - Reading a vector backwards" << endl;
	cout << "October 31, 2016" << endl;
	cout << endl;
	cout << endl;

	int numOfValues;
	while(true)
	{
		cout << "Please enter the number of values you need stored : ";
		if(cin >> numOfValues && numOfValues >= 1 && numOfValues <= 200) break;

		if(!cin)
		{
			cin.clear();
			cin.ignore(1000, '\n');		
		}
		cout << "Invalid number or number out-of range. Please try again\n\n";
	}

	vector<double> val;
	val.resize(numOfValues);

	for(i = val.size() - 1; i >= 0; i--)
	{
		cout << "- Enter value " << i + 1 << " : "; 
		
		if(!(cin>> val[i]))
		{
			i++;
			cin.clear();
			cin.ignore(1000, '\n');
			cout << "Invalid value. Please try again.\n\n";
		}
	}

	cout << endl;
	cout << "The array you entered : ";

	for(i = 0; i < val.size(); i++)
	{
		cout << val[i];
		if(i < (val.size() - 1)) cout << ", ";
	}

	cout << endl;

	cin.ignore();
	cin.get();
	return 0;
}

Kaitlin Stevers (kns2872) on Cplusplus forum
Exercise 9A - Reading a vector backwards
October 31, 2016

Please enter the number of values you need stored : 12
- Enter value 12 : 33
- Enter value 11 : 76
- Enter value 10 : 24
- Enter value 9 : 85
- Enter value 8 : 42
- Enter value 7 : 55
- Enter value 6 : 22
- Enter value 5 : 15
- Enter value 4 : 64
- Enter value 3 : 34
- Enter value 2 : 100
- Enter value 1 : 22

The array you entered : 22, 100, 34, 64, 15, 22, 55, 42, 85, 24, 76, 33

[ENhkSL3A]

SakurasouBusters can I ask you something?

[SakurasouBusters]

Sure, no hesitation.

[ENhkSL3A]

Did you read the part where I said, "I need to know how to use the member function

vest.reverse(); 

in order to read the vector backwards."

[SakurasouBusters]

You are asking us to use std::vector of course. And read the vector backwards.
But your code shows that you are using a normal array.

Edit : Should you change the title to

"Reading an array backwards!"

?

[ENhkSL3A]

I'm so confused.......... omg... Now I feel stupid. I kept thinking vector and saying it but it is array... Humm. Newbee question, what is the difference in the two?? & How do I read the array backwards and output it.

[JLBorges]

> what is the difference in the two??

See: https://cal-linux.com/tutorials/vectors.html


> How do I read the array backwards and output it.

To iterate through an array (or any standard sequence) backwards, where seq is the sequence:

// C++14
for( auto iter = std::rbegin(seq) ; iter != std::rend(seq) ; ++iter ) { /* do something with *iter */ }

http://en.cppreference.com/w/cpp/iterator/rbegin

For instance:

#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <array>
#include <iterator>

int main()
{
    const int a[] { 0, 1, 2, 3, 4, 5 } ;
    for( auto iter = std::rbegin(a) ; iter != std::rend(a) ; ++iter ) std::cout << *iter << ' ' ;
    std::cout << '\n' ;

    const std::vector<double> b { 0.1, 2.3, 4.5, 6.7, 8.9 } ;
    for( auto iter = std::rbegin(b) ; iter != std::rend(b) ; ++iter ) std::cout << *iter << ' ' ;
    std::cout << '\n' ;

    const std::list<std::string> c { "zero", "one", "two", "three", "four", "five" } ;
    for( auto iter = std::rbegin(c) ; iter != std::rend(c) ; ++iter ) std::cout << *iter << ' ' ;
    std::cout << '\n' ;

    const std::array<long,6> d { { 10, 11, 12, 13, 14, 15 } } ;
    for( auto iter = std::rbegin(d) ; iter != std::rend(d) ; ++iter ) std::cout << *iter << ' ' ;
    std::cout << '\n' ;
}

http://coliru.stacked-crooked.com/a/73f1bca671a0d74a

[ENhkSL3A]

I'm sorry but the std::cout << is throwing me off. Is that the same as cout <<? Is that what you do when you do not use, using namespace std;

[JLBorges]

> Is that what you do when you do not use, using namespace std;

Yes.
More information: http://www.cplusplus.com/forum/beginner/142171/#msg750694

#include <iostream> // std::cout
#include <iterator> // std::rbegin, std::rend

int main()
{
    using namespace std ; // ****

    const int a[] { 0, 1, 2, 3, 4, 5 } ;
    for( auto iter = rbegin(a) ; iter != rend(a) ; ++iter ) cout << *iter << ' ' ;
    cout << '\n' ;
}

[ENhkSL3A]

I'm still unsure what to do in my case. Yours uses an actual set of numbers programmed in. In my case the user is entering the array in and I need to spit it out forwards and then backwards. Unfortunately, no one has this anywhere I've looked. :(

[ENhkSL3A]

I need some advice soon. Please make sure it works and makes since with my code. Thanks guys.

[JLBorges]

#include <iostream>

int main()
{
    const int ARRAY_SIZE = 50;
    int val[ARRAY_SIZE];

    int num_values;
    std::cout << "Please enter the number of values [0," << ARRAY_SIZE
              << "] you need stored.\n" ;
    std::cin >> num_values;

    if( num_values <= ARRAY_SIZE )
    {
        for( int i = 0; i < num_values; ++i )
        {
            std::cout << "Enter an integer value: ";
            std::cin >> val[i];
        }

        std::cout << "Here are the values you entered:\n";
        for( int i = 0; i < num_values; ++i ) std::cout << val[i] << ' ' ;
        std::cout << '\n' ;

        std::cout << "Here are the values backwards:\n";
        int pos_last = num_values - 1 ; // position of the last value that was entered
        for( int i = 0; i < num_values; ++i ) std::cout << val[ pos_last - i ] << ' ' ;
        std::cout << '\n' ;
    }
}

[ENhkSL3A]

Thank you sooooooo much!!!! I've been trying to figure this out for hours... Obviously I failed lol It makes since now though! so, THANK YOU!