For user input, spaces between coefficients, operands, exponent and term are opt

Question

For user input, spaces between coefficients, operands, exponent and term are
optional.

For simplicity, you can assume the following in the input format:
1. Coefficients and exponents are within the range of int type integers.
2. The polynomial is input in the format of decreasing order of exponent, with like-terms combined already.

So, user input could look like these possible situations for example:

1) 4x^3 - 2x^2 + 3x + 1

2) -4x^2 + 4x + 1

3) 4 x ^ 29 + 3 x ^ 9 - 2 x ^ 8 - 2 x ^ 6 + 10 x ^ 2 - x + 1

Since spaces do not matter, please write C++ code that can extract the coefficients and exponents of each term of ANY polynomial where the user inputs a string as the polynomial.

ALSO, library use is very limited, so cstring, cctype, cstdlib, string are alright.

Consider the following implementation declaration for Polynomial using pointers: struct ATerm {int Coefficient; int ATerm* Next; Exponent; typedef ATerm* Polynomial

Explanation / Answer

#include <iostream>
#include <string>
#include <cstdlib>
#include <cctype>
using namespace std;

struct Aterm
{
int Coefficient;
int Exponent;
Aterm* Next;
};
typedef Aterm* Polynomial;
int main()
{
int mulf,tval;
string poly,cpoly,tempstr;
getline(cin,poly);
Polynomial head,temp1;
for(int i=0; i<poly.size(); i++) // Clearing out all spaces
{
if(poly[i]!=' ')
cpoly.push_back(poly[i]);
}
if(isdigit(cpoly[0]))
mulf=1;
for(int i=0; i<cpoly.size(); i++)
{
Polynomial temp=new Aterm();
if(i!=0)
{
temp1->Next=temp;
temp1=temp;
}
else
{
head=temp;
temp1=temp;
}
temp->Exponent=1;
temp->Next=NULL;
if(cpoly[i]=='+')
{
mulf=1;
i++;
}
else if(cpoly[i]=='-')
{
mulf=-1;
i++;
}
if(cpoly[i]!='x'&&cpoly[i]!='X') //Finding Coefficient
{
tval=0;
while(i<cpoly.size()&&isdigit(cpoly[i]))
{
tval=(tval*10)+cpoly[i]-48;
i++;
}
tval*=mulf;
temp->Coefficient=tval;
}
else
temp->Coefficient=mulf;
if(i==cpoly.size())
{
temp->Exponent=0;
break;
}
if(i+1==cpoly.size())
break;

if(cpoly[i+1]!='^')
continue;
i+=2;
if(cpoly[i]=='+')
{
mulf=1;
i++;
}
else if(cpoly[i]=='-')
{
mulf=-1;
i++;
}
tval=0;
while(i<cpoly.size()&&isdigit(cpoly[i])) //Finding Exponent
{
tval=(tval*10)+cpoly[i]-48;
i++;
}
//tval*=mulf;
temp->Exponent=tval;
i--;
}
return 0;
}

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