Input strings and display reversely using for loops with arrays

Question

What I want to do is to enter a number of loops , then all the entered words will be displayed on reverse . I tried numbers to display on reverse , and it works . But , I don't know what to change in the codes . I'm not good in c++ , so I'm practicing . Thanks for helping me =)

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

int main()
{
    int x, y;
    string a[y];
    cout << "Enter number: ";
    cin >> x;
    x=x-1;
    for (y=0; y<=x; y++)
    {
        cout << y+1 << ". ";
        cin >> a[y];
    }
    for (y=x; y>=0; y--)
    {
        cout << a[y] << endl;
    }
    return 0;
}

do yo want to input a string and then print that string in reverse order ?? — Asis
– Asis, Commented Oct 12, 2014 at 9:14
This is undefined: string a[y]; you'll need to put this line at least after cin >> x; x=x-1; — πάντα ῥεῖ
– πάντα ῥεῖ, Commented Oct 12, 2014 at 9:26
@kempoy211 As I pointed out in my post C++ has no Variable Length Arrays. So you marked an answer as the best that uses VLA. That is the code presented in the answer does not satisfy the C++ Standard and can be not compiled by other compilers. — Vlad from Moscow
– Vlad from Moscow, Commented Oct 12, 2014 at 12:01
@VladfromMoscow I'm sorry, I thought I could mark two answers. Sorry — kempoy211
– kempoy211, Commented Oct 15, 2014 at 13:07

Vlad from Moscow · Accepted Answer · 2014-10-12 09:26:03Z

1

Your ptogram is invalid. For example you are declaring array a

string a[y];

while variable y was not initialized

int x, y;

C++ does not allow to define Variable Length Arrays.

So instead of an array it would be better to use standard container std::vector

The program could look the following way

#include <iostream>
#include <vector>
#include <string>

int main() 
{
    std::cout << "Enter number: ";

    size_t n = 0;
    std::cin >> n;

    std::vector<std::string> v;
    v.reserve( n );

    for ( size_t i = 0; i < n; i++ )
    {
        std::cout << i + 1 << ". ";

        std::string s;
        std::cin >> s;
        v.push_back( s );
    }

    for ( size_t i = n; i != 0; i-- )
    {
        std::cout << v[i-1] << std::endl;
    }

    return 0;
}

For example if the input looks like

4
Welcome
to
Stackoverflow
kempoy211

then the output will be

kempoy211
Stackoverflow
to
Welcome

answered Oct 12, 2014 at 9:26

Vlad from Moscow

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4 Comments

kempoy211 Over a year ago

THANK YOU VERY MUCH ! Do you know what's the best website to learn more on C++ ? Sorry for follow-up question . Thank you ! =)

Vlad from Moscow Over a year ago

@kempoy211 I do not use web sites to learn C++. I only see through web sites when I have a question. So I can not advice a web site for learning C++.

kempoy211 Over a year ago

Can I send to the database all entered strings using the preprocessor fstream ? And then , when I want to view my database , can I send them back to the program ? I mean , display or view it .

Vlad from Moscow Over a year ago

@kempoy211 What is "preprocessor fstream"? Of course you can write amd read files.

ravi · Accepted Answer · 2014-10-12 09:16:55Z

0

You can use std::reverse from algorithm library in C++. With that you don't need to write these bulky loops

EDITED:-

If you just want a reverse traversal and print your string below is the Pseudo code:-

for ( each string str in array )
{
for ( int index = str.length()-1; index >= 0; index -- )
cout << str[index];
}
cout <<endl;
}

edited Oct 12, 2014 at 9:16

answered Oct 12, 2014 at 9:10

ravi

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1 Comment

quantdev Over a year ago

Not really, std::reverse will change the container, the OP asks for a reverse traversal

Spikatrix · Accepted Answer · 2014-10-12 09:31:18Z

0

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

int main()
{
    int x, y;
    cout << "Enter number: ";
    cin >> x;
    string a[x];  //this should be placed after cin as x will then be initialized
for (y=0; y<x; y++)
    {
        cout << y+1 << ". ";
        cin >> a[y];
    }
for (y=x-1; y>=0; y--)  // x-1 because array index starts from 0 to x-1 and not 0 to x
    {
        cout << a[y] << endl;
    }
return 0;
}

Output:

Enter Number: 5
1. one
2. two
3. three
4. four
5. five
five
four
three
two
one

answered Oct 12, 2014 at 9:31

Spikatrix

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1 Comment

kempoy211 Over a year ago

Can I send the entered & scanned string to the database using the preprocessor fstream ? TIA.

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