How do i get rid of the last comma? c is reading from a file and reading the numbers backwards-CodePudding

C is reading from a file and printing out the numbers backwards. i got rid of the comma when it prints out forward. But I cannot figure out how to do the same for back wards.

so far this is what I have:

cout<<"Forwards: ";
for (int i=0; i<cnt; i  ){
    cout<<setprecision(2)<< fixed;
    if (i == cnt - 1)
    {
        cout << arr[i];
    }
    else
    {
        cout << arr[i] << ", ";
    }
}
cout<<endl;
//printing backwards 
cout << "Backwards: ";
for (int i=cnt-1; i>=0; i--){
    cout<<setprecision(2)<< fixed;
    if (i == cnt   1)
    {
        cout << arr[i];
    }
    else
    {
        cout << arr[i] << ", ";
    }

the forwards part comes out correct: 1.00, 2.00, 3.00, 4.00, 5.00, 6.00, 7.00, 8.00, 9.00, 10.00

but the backwards is what prints out

10.00, 9.00, 8.00, 7.00, 6.00, 5.00, 4.00, 3.00, 2.00, 1.00,

how do I get rid of that last comma

CodePudding user response：

Try something like this:

bool first_item = true;
for (unsigned int i = 0u; i < LIMIT;   i)
{
    if (! first_item)
    {
        std::cout << ", ";
    }
    first_item = false;
    std::cout << number;
}
std::cout << "\n";

The above code fragment works regardless of the direction, ascending or descending.

The important part is the "flag" to determine if the first item has been printed.

CodePudding user response：

In the forward-moving loop, if (i == cnt - 1) is checking if i is on the last element of the array.

In the backward-moving loop, you want to check if i is on the first element, but if (i == cnt 1) will never be true for that check, as cnt 1 is out of bounds. The first element is at index 0, so use if (i == 0) instead:

cout << "Forwards: ";
cout << setprecision(2) << fixed;
for (int i = 0; i < cnt;   i){
    if (i == cnt - 1){
        cout << arr[i];
    }
    else{
        cout << arr[i] << ", ";
    }
}
cout << endl;

cout << "Backwards: ";
cout << setprecision(2) << fixed;
for (int i = cnt-1; i >= 0; --i){
    if (i == 0){
        cout << arr[i];
    }
    else{
        cout << arr[i] << ", ";
    }
}
cout << endl;

Alternatively, print the 1st output value outside of the loop, and then start the loop on the 2nd output value:

cout << "Forwards: ";
cout << setprecision(2) << fixed;
cout << arr[0];
for (int i = 1; i < cnt;   i){
    cout << ", " << arr[i];
}
cout << endl;

cout << "Backwards: ";
cout << setprecision(2) << fixed;
cout << arr[cnt-1];
for (int i = cnt-2; i >= 0; --i){
    cout << ", " << arr[i];
}
cout << endl;