Degree: Polynomial Class (Odd Cases for User Input Expected) - c++

Question

I have a polynomial class that prompts the user to enter values to be put into a vector of integers (vector<int> vect_poly). I'm trying to think of a way to detect the degree of the polynomial for cases where the user does something like this in the while loop:
0↵0↵0↵0↵4↵0↵0↵0↵0 ← x^4 (degree=4)
(OR)
0↵0↵0↵0↵0↵0↵0↵0↵0 ← (degree=0)
(OR)
4↵0↵0↵0↵0↵0↵0↵0↵0 ← x^0 (degree=0)
(OR)
0↵0↵0↵0↵0↵0↵0↵0↵4 ← x^8 (degree=8)
I'm really just looking for a slick algorithm.
What about this:
int degree()
{
int d = 0;
for ( int i = 0; i < 100; i++ )
if ( coef[i] != 0 ) d = i;
return d;
}

Answer 1

If u have this vector where user have enter the value of coefficient, you can traverse the vector from index 0 to the last element (Assuming user will enter the value of coefficient in correct order), and just save the value of last index whose value is not zero.
int degreeOfPolynomial=0;
for(int i=0 ; i < vect_poly.size() ; i++)
{
if(vect_poly[i] != 0)
degreeOfPolynomial = i;
}
After execution of above part of code, degreeOfPolynomial will store right value of degree of polynomial.

Answer 2

Why not just keep track of it?
std::vector<int> polynomial;
int degree = 0;
int inputs = 0;
int coefficient;
while (std::cin >> coefficient)
{
polynomial.push_back(coefficient);
if (coefficient != 0)
{
degree = inputs;
}
inputs++;
}

Answer 3

I see two options:
Simply copy the input into the vector, then search for the last non-zero and truncate the vector after that.
Copy input into a temporary vector, and each time a non-zero is entered, move-append the temporary vector to vect_poly, like this:
std::vector<int> temp;
int n;
while (std::cin >> n) {
temp.push_back(n);
if (n != 0) {
vect_poly.insert(vect_poly.end(), temp.begin(), temp.end());
temp.clear();
}
}
That way, you get everything except the trailing zero sequence in vect_poly.
EDIT
3. You can also keep the 0s in a counter:
int n;
size_t zeroes = 0;
while (std::cin >> n) {
if (n == 0) {
++zeroes;
} else {
vect_poly.insert(vect_poly.end(), zeroes, 0);
vect_poly.push_back(n);
zeroes = 0;
}
}

Answer 4

You can use a local variable to keep track of the max, and each time the user presses enter, you compare their input to the current max value.
int max=0;
while(1)
{
int input=0;
std::cin>>input;
if(input>max)
{
max=input;
}
}
Of course with some breakout condition so the loop doesn't run forever. You could try to mess with the ternary operator at the if statement, but I see little value in that.
EDIT: if you want to know the last set value (ie degree) of a previously generated but essentially random vector as quickly as possible, run a loop like this:
int max=0;
for(int k= myvec.size()-1; k>=0; k--)
{
if(myvec[k]>0)
{
max=k;
break;
}
}