Can't figure out this stack output c++ - c++

Question

So I have a stack example I created following a tutorial using the stack library
stack<string> custs;
custs.push("george");
custs.push("louie");
custs.push("florence");
// cout << "size" << custs.size() << endl;
if (!custs.empty()) {
for (int i = 0; i <= custs.size(); i++) {
cout << custs.top() << endl;
custs.pop();
}
}
I ran this and got the output:
florence
louie
My question is why isn't it outputting George as well? The program outputs the top data then pops it. This means it should output Gorge then pop it after. Why doesn't this happen? initially the code was i < cust.size so I thought because i is not less than 1 it would not ouput. So I switched it to <= and it still doesn't output George. How come?

Answer 1

It is because you are both increasing i and reducing the size of the stack in the loop.
You can rewrite your loop like this:
while (!custs.empty()) {
cout << custs.top() << endl;
custs.pop()
}

Answer 2

Here is a step by step explanation of what is happening so you can understand it better:
First, i starts as 0, and custs.size() returns 3. Since 0 <= 3 is true, the body of the loop executes, printing "florence" and removing it from the stack.
On the second iteration, i equals 1, and custs.size() returns 2, because you had 3 items but you removed one. Since 1 <= 2 is true, the body of the loop executes again, printing "louie" and removing it from the stack.
Then, i equals 2, and custs.size() returns 1, because you already removed 2 elements. Since 2 <= 1 is false, the body of the loop doesn't execute, and the loop ends.
As you can see, the problem is that your loop's condition changes on each iteration. There are a couple of ways to fix this:
int s = custs.size();
for (int i = 0; i < s; i++) {
cout << custs.top() << endl;
custs.pop();
}
By doing that, you store the original size of the stack, so you can iterate without problems.
Another solution would be to check if the stack is empty on each iteration with a while loop:
while (!custs.empty()) {
cout << custs.top() << endl;
custs.pop();
}
By doing that, you check if there are any elements left to print each time.
Hope this helps!

Answer 3

When you use for loop like this
for (int i = 0; i <= custs.size(); i++) {
cout << custs.top() << endl;
custs.pop();
}
it loops directly till the size of stack which decreases in each iteration.
which in my opinion is the main reason your code is not working. I rewrite this as
int z = custs.size() ;
for(int i=0;i<=z;i++)
{
cout<<custs.top()<<endl;
custs.pop();
}
and it worked perfectly fine. In my opinion, the best approach is to use while loop like this
while(!custs.empty())
{
cout<<custs.top()<<endl;
custs.pop();
}