CODEWITHSUNDEEP
c++
Gulzar
Gulzar

Reputation: 21

why string variable "sum" is not storing any data and program is not giving any output

    int l, s, j, k, carry=0;
    string num1, num2, sum;

    cin >> num1 >> num2;
    l = num1.size();
    s = num2.size();

    for(j=l-1; j>=0; j--)
    {
        k = (num1[j]-'0') + (num2[j]-'0') + carry;
        cout << k<<endl;
        carry = k/10;
        k%=10;
        sum[j]= '0' + k;
    }

    cout  << sum << endl;

I am trying to add two numbers(both have same digit length) using strings. It is not giving any output.

Upvotes: 1

Views: 95

Answers (1)

alexeykuzmin0
alexeykuzmin0

Reputation: 6440

Just after the variable declaration your sum variable is an empty string. You're trying to access jth element of it - this is the array index overflow and is an undefined behavior.

The solution is to initialize your string with something or use concatenate instead of changing the character, like this:

sum += (char)('0' + k);

UP: Such fix will write the result to the string in the reversed order, so, to obtain the correct string, you should also add

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

after the loop.

And also, your code assumes that the sum length is exactly the same as the lengths of both arguments which may be wrong.

Upvotes: 4

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