如何在C ++中将字符串数据存储在字符串2D数组中

Question

I want to store data in the first element at the first index of 2D array t[0][0]! I write this code:

int main()
{
    string input;
    cout << "Enter string of code:\n";
    cin >> input;
    queue < string > m;
    string t[100][3];
    while (input != "^")
    {
        int i = 0;

        t[i][0] = input;
        m.push(t[i][0]);
        if (input == " ")
        {
            t[i + 1][0];
            break;
        }

        cin >> input;
        i++;

    }
    int c = 1;
    while (!m.empty())
    {
        int i = 0;
        t[i][0] = m.front();
        string temp;
        temp = t[i][0];
        t[i][1] = check(temp);
        //cout <<c<<" "<<t[i][0]<<" Is: " << t[i][1] << endl;
        c++;
        m.pop();
        i++;
    }
    cout << endl;

    cout << c << " " << t[0][0] << " Is: " << t[0][1] << endl;

    system("Pause");
    return 0;
}

I have problem with this statement

cout << c << " " << t[0][0] << " Is: " << t[0][1] << endl;

this doesn't print the value in the array!

Answer 1

Declare and initialize i above the while loop, like this:

int i = 0;
while (!m.empty())
{
    t[i][0] = m.front();
    ...

---

Let me explain what happens (in your code) here:

while (!m.empty())
{
    int i = 0;
    t[i][0] = m.front();
    string temp;
    temp = t[i][0];
    t[i][1] = check(temp);
    //cout <<c<<" "<<t[i][0]<<" Is: " << t[i][1] << endl;
    c++;
    m.pop();
    i++;
}

Every time you enter the body of the loop, a variable named i is declared and initialized to 0. The scope of i is the body of the loop.

You increment i at the end of the loop, but as soon as the loop runs again, i will be again be initialized to 0 (you also re-declare it). So if we were in the second loop, you would want to i to have a value of 1, but because you initialize to 0 every time you enter the loop, it will always have a value of 0 as you are executing the body of the loop.

---

Moreover, this line:

t[i + 1][0];

should issue a warning of this kind:

main.cpp:22:23: warning: expression result unused [-Wunused-value]
            t[i + 1][0];
            ~~~~~~~~ ~^

I got by compiling your code like this:

g++ -Wall main.cpp

where the flag Wall enables all warnings, pretty cool, make this your friend.

It is helpful, as it happens now, since that line does nothing that has impact on your code.

---

PS: Of course, I don't know what is the check() you have in your code, so this is all I can say .