Swapping strings (string subscript out of range error)

Question

I wanted to make a program that assign a string to another string on reverse without using any builtin functions but i got this error,how can i solve it. image

#include <iostream>

using namespace std;
int main()
{
    string a, b;
    
    cin >> a;
    for (int i = 0; i < a.size(); i++)
    {
        b[i] = a[a.size() - 1 - i];
    }
    cout << b;

}

When you get that error press Retry and break into the debugger. Then switch the "Stack Frame" on the debug toolbar to your code to see the exact line of your code that was running when the code crashed. — drescherjm, Dec 19 '20 at 15:41
[Why is “using namespace std;” considered bad practice?](https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice) — Gary Strivin', Dec 19 '20 at 17:18

score 1 · Answer 1 · edited Dec 20 '20 at 01:03

The code does not allocate space for the string b, your code assumes that b has a.size() as size. Which is not true insert the statement b.resize(a.size()) before the loop

Full code:

#include <iostream>

using namespace std;
int main()
{
    string a, b;
    
    cin >> a;
    b.resize(a.size());
    for (int i = 0; i < a.size(); i++)
    {
        b[i] = a[a.size() - 1 - i];
    }
    cout << b;

}

score 1 · Answer 2 · answered Dec 19 '20 at 15:25

Change this

b[i] = a[a.size() - 1 - i];

to this

b += a[a.size() - 1 - i];

Strings (and vectors) do not automatically adjust their size when you use []. If your string has size zero you need to use push_back, resize, += or similar to add characters to it.

score 0 · Answer 3 · answered Dec 19 '20 at 15:32

0

Replace your code with the following:

#include <iostream>

using namespace std;
int main()
{
  string a="", b="";

cin >> a;
for (int i = 0; i < a.size(); i++)
{
    b+= a[a.size() - 1 - i];
}
cout << b;

return 0;
}

answered Dec 19 '20 at 15:32

nissim abehcera

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Swapping strings (string subscript out of range error)

3 Answers3