Extra Characters Inserted Into Array

Question

I'm a C++ beginner and wrote a program to check if two phrases are anagrams. The characters are being read one at a time and stored in an array. I have everything working, except in some cases, extra characters are being inserted into the array.

For example, if I enter the phrases aabb and abba, this is the output of the program:

Enter two lines that might be anagrams:
--> aabb
--> abba
String A is aabb
String B is abbai?
The two strings are NOT anagrams.

They should be anagrams, but for some reason, i? is added into the array, causing the phrases to not be anagrams. I'm probably overlooking a simple mistake in the code, but would really appreciate any feedback.

Here is the code:

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

int check_anagram(char [], char []);

int main()
{
    char ch, a[60], b[60];
    int flag, i;

    cout << "Enter two lines that might be anagrams:" << endl;
    cout << "--> ";

    cin.get(ch);
    ch = tolower(ch);

    i = 0;
    while (ch != '\n')
    {
        if (ch > '@') {
            a[i] = ch;
            i++;
        }
        cin.get(ch);
        ch = tolower(ch);
    }

    cout << "--> ";

    cin.get(ch);
    ch = tolower(ch);

    i = 0;
    while (ch != '\n')
    {
        if (ch > '@') {
            b[i] = ch;
                i++;
        }
        cin.get(ch);
        ch = tolower(ch);
    }

    flag = check_anagram(a, b);

    cout << "String A is " << a << endl;
    cout << "String B is " << b << endl;

    cout << "The two strings ";
    if (flag == 1)
        cout << "ARE";
    else
        cout << "are NOT";
    cout << " anagrams." << endl << endl;

    return 0;
}

int check_anagram(char a[], char b[])
{
    int first[26] = {0}, second[26] = {0}, c = 0;

    while (a[c] != '\0')
    {
        first[a[c]-'a']++;
        c++;
    }

    c = 0;

    while (b[c] != '\0')
    {
        second[b[c]-'a']++;
        c++;
    }

    for (c = 0; c < 26; c++)
    {
        if (first[c] != second[c])
            return 0;
    }

    return 1;
}

Thanks in advance!

Answer 1

You just need to terminate the two character arrays with '\0' because the logic in check_anagram treats both arrays as NULL-terminated.

   ..
   while (ch != '\n')
   {
      if (ch > '@') {
         a[i] = ch;
         i++;
      }
      cin.get(ch);
      ch = tolower(ch);
   }

   a[i] = '\0';     // <<<<<<<< Add this line
   cout << "--> ";

   cin.get(ch);
   ch = tolower(ch);

   i = 0;
   while (ch != '\n')
   {
      if (ch > '@') {
         b[i] = ch;
         i++;
      }
      cin.get(ch);
      ch = tolower(ch);
   }

   b[i] = '\0';     // <<<<<<<< Add this line
   ..

Here is the result:

Enter two lines that might be anagrams:
--> aabb
--> abba
String A is aabb
String B is abba
The two strings ARE anagrams.