CODEWITHSUNDEEP
c++
NullPoiиteя
NullPoiиteя

Reputation: 57312

Random ascii char's appearing

I was trying to write a program that stores the message in a string backwards into a character array, and whenever I run it sometimes it successfully writes it backwards but other times it will add random characters to the end like this:

input: write this backwards

sdrawkcab siht etirwˇ

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

int main()
{
 string message;
 getline(cin, message);
 int howLong = message.length() - 1;
 char reverse[howLong];
 for(int spot = 0; howLong >= 0; howLong--)
 {
   reverse[spot] = message.at(howLong);
   spot++;
 }
 cout << reverse;
 return 0;
}

Upvotes: 1

Views: 382

Answers (4)

mmisu
mmisu

Reputation: 393

Use a proper C++ solution.

Inline reverse the message:

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

using namespace std;

int main() {
    string message;
    getline(cin, message);

    //inline reverse the message
    reverse(message.begin(),message.end());

    //print the reversed message:
    cout << message << endl;
    return 0;
}

Reverse a copy of the message string:

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

using namespace std;

int main() {
    string message, reversed_message;
    getline(cin, message);

    //reverse message
    reversed_message = message;
    reverse(reversed_message.begin(), reversed_message.end());

    //print the reversed message:
    cout << reversed_message << endl;
    return 0;
}

If you really need to save the reversed string in a C string, you can do it:

char *msg = (char *)message.c_str();

but, as a rule of thumb use C++ STL strings if you can.

Upvotes: 1

Mark Ransom
Mark Ransom

Reputation: 308111

Instead of reversing into a character buffer, you should build a new string. It's easier and less prone to bugs.

 string reverse;
 for(howlong; howLong >= 0; howLong--)
 {
   reverse.push_back(message.at(howLong));
 }

Upvotes: 1

ipc
ipc

Reputation: 8143

Since you can't declare an array with a length that is only known at runtime, you have to use a container instead.

std::vector<char> reverse(message.length());

Or better, use std::string. The STL also offers some nice functions to you, for example building the reversed string in the constructor call:

std::string reverse(message.rbegin(), message.rend();

Upvotes: 2

Mark Wilkins
Mark Wilkins

Reputation: 41232

The buffer reverse needs to be message.length() + 1 in length so that it can store a null termination byte. (And the null termination byte needs to be placed in the last position in that buffer.)

Upvotes: 4

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