Question

#include<iostream>
#include<string.h>
using namespace std;
char * reverse (char *);
int main()
{
    char * a;
    cout<<"enter string"<<endl;
    gets(a);
    cout<<a;
    cout<<"the reverse of string is"<<reverse(a);
    return 0;
}
char * reverse (char * b)
{
    int i,j=strlen(b);
    for(i=0;b[i]!='\0';i++)
    {
        char temp;
        temp=b[j-i-1];
        b[j-i-1]=b[i];
        b[i]=temp;
    }
    return b;
}

This program is giving no compile time error.But it does give run time error and does not give desired output. Please explain the cause.As I am not that much good in C++ so please forgive me if my question is not upto mark.

Answer 1

You are not allocating memory for the string. gets doesn’t allocate memory for you, so you’re just reading into some random location – results are undefined.

Apart from that, there are more problems:

• This is tagged C++ but it’s more like C with cout (using string would be a better idea)
• You are using gets instead of fgets. gets is quite dangerous and should be avoided.