Question

What is happening to my palindrome program? C++.

Here is what my code does. I have to strings. The user inputs into one of them. I use a for loop to enter the string into a second one in reverse. Then, I use strcmp to see if they are the same. If the output of strcmp is 0 the answer is trye, otherwise false. For some reason something is going really wrong with my copyString. I tried copying my for loop directly from a website to see if I was doing it wrong and i still get a weird value inside copString

#include<iostream>
#include<string.h>
#include<string>

using namespace std;

int main() {
   char string1[20], copyString[20];

   int i,x, length=0,j,flag=0;

   cout << "Enter a string: ";
   gets_s(string1);

   length = strlen(string1) - 1;

   for (i = length, j = 0; i >= 0; i--, j++) {
       copyString[j] = string1[i];
   }

   flag = (strcmp(string1, copyString));

   cout << flag << endl << "here is 1: " <<string1 << endl << endl <<copyString;

   if (flag == 0)
       cout << "True";
   else
       cout << "False";

}

Answer 1

#include<iostream>
#include<string.h>
#include<string>

using namespace std;

int main() {
    char string1[20], copyString[20];

    int i, x, length = 0, j, flag = 0;

    cout << "Enter a string: ";
    gets_s(string1);

    length = strlen(string1) - 1;

    for (i = length, j = 0; i >= 0; i--, j++) {
        copyString[j] = string1[i];
    }
    copyString[j] = '\0';   // we have to end a string with '\0'. null-terminating character.

    flag = (strcmp(string1, copyString));

    cout << flag << endl << "here is 1: " << string1 << endl << endl << copyString;

    if (flag == 0)
        cout << "True";
    else
        cout << "False";
}