C++ Cin input to array

Question

I am a beginner in c++ and I want to enter a string as character by character into an array , so that I can implement a reverse function .. However unlike C when the enter is hit a '\n' is not insterted in the stream.. how can I stop data from being entered ?

my code is :

#include<iostream>
#include<array>
#define SIZE 100
using namespace std;

char *reverse(char *s)
{
    array<char, SIZE>b;
    int c=0;
    for(int i =(SIZE-1);i>=0;i--){
        b[i] = s[c];
        c++;
    }

    return s;
} 

int main()
{
    cout<<"Please insert a string"<<endl;
    char a[SIZE];
    int i=0;
    do{
        cin>>a[i];
        i++;
    }while(a[i-1]!= '\0');

    reverse(a);

    return 0;
}

What is your reverse function supposed to do? I think your not asking yourself the right question — Treycos
– Treycos, Commented Oct 6, 2016 at 14:43
I solved it by reading it into a string .. and knowing the string length I reversed it by looping .. thanks all — Dylan Galea
– Dylan Galea, Commented Oct 7, 2016 at 10:51

Community · Accepted Answer · 2017-05-23 10:31:09Z

7

When you read character by character, it really reads characters, and newline is considered a white-space character.

Also the array will never be terminated as a C-style string, that's not how reading characters work. That means your loop condition is wrong.

To begin with I suggest you start using std::string for your strings. You can still read character by character. To continue you need to actually check what characters you read, and end reading once you read a newline.

Lastly, your reverse function does not work. First of all the loop itself is wrong, secondly you return the pointer to the original string, not the "reversed" array.

To help you with the reading it could be done something like

std::string str;
while (true)
{
    char ch;
    std::cin >> ch;
    if (ch == '\n')
    {
        break;  // End loop
    }

    str += ch;  // Append character to string
}

Do note that not much of this is really needed as shown in the answer by Stack Danny. Even my code above could be simplified while still reading one character at a time.

edited May 23, 2017 at 10:31

CommunityBot

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answered Oct 6, 2016 at 14:43

Some programmer dude

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2 Comments

Dylan Galea Over a year ago

why this does not work ? #include<iostream> #include<array> #define SIZE 100 using namespace std; char *reverse(char *s){ array<char, SIZE>b; int c=0; for(int i =(SIZE-1);i>=0;i--){ b[i] = s[c]; c++; } return s; } int main(){ cout<<"Please insert a string"<<endl; char a[SIZE]; int i=0; do{ cin>>a[i]; i++; }while(a[i-1]!= '\0'); reverse(a); return 0; }

Some programmer dude Over a year ago

@DylanGalea To begin with, you have no statement setting any element in a to '\0'. Do learn how to use a debugger, and how to step through your code line by line while monitoring variables and their values.

Stack Danny · Accepted Answer · 2016-10-06 14:43:35Z

6

Since you tagged your question as C++ (and not C) why not actually solve it with the modern C++ headers (that do exactly what you want, are tested, save and work really fast (rather than own functions))?

#include <string>
#include <algorithm>
#include <iostream>

int main(){
    std::string str;
    std::cout << "Enter a string: ";
    std::getline(std::cin, str);

    std::reverse(str.begin(), str.end());

    std::cout << str << std::endl;

    return 0;
}

output:

Enter a string: Hello Test 4321
1234 tseT olleH

answered Oct 6, 2016 at 14:43

Stack Danny

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