Intuition
We are told to micmic the polynomial multiplication. Such as, $(x-1)(x-1)=x^2-2x+1$, etc.
So, if you do it correctly, it would be correct.
p.s. You should use long long in this question.
Sample Code
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| #include <bits/stdc++.h>
using namespace std;
#define ll long long
void addPoly(vector<ll> &poly1, vector<ll> &poly2, ll val = 1, int shift = 0)
{
vector<ll> res(max(poly1.size(), poly2.size() + shift), 0);
for (ll i = 0; i < poly1.size(); i++)
res[i] = poly1[i];
for (ll i = 0; i < poly2.size(); i++)
res[i + shift] += poly2[i] * val;
poly1 = res;
}
void multiply(vector<ll> &poly1, vector<ll> &poly2)
{
vector<ll> res(poly1.size() + poly2.size(), 0);
for (ll i = 0; i < poly2.size(); i++)
addPoly(res, poly1, poly2[i], i);
poly1 = res;
while (poly1.back() == 0)
poly1.pop_back();
}
int main()
{
int n;
while (cin >> n)
{
vector<ll> res(1, 1);
for (ll i = 0; i < n; i++)
{
vector<ll> temp(2, 1);
cin >> temp[0];
temp[0] = -temp[0];
multiply(res, temp);
}
for (ll i = res.size() - 1; i >= 0; i--)
{
if (!i)
{
if (i == res.size() - 1)
;
else if (res[i] >= 0)
cout << " + ";
else
{
cout << " - ";
res[i] = -res[i];
}
cout << res[i];
continue;
}
if (!res[i] || i == res.size() - 1)
;
else if (res[i] < 0)
{
cout << " - ";
res[i] = -res[i];
}
else if (res[i] > 0)
cout << " + ";
if (res[i] > 1)
cout << res[i];
if (res[i])
{
cout << "x";
if (i > 1)
cout << "^" << i;
}
}
cout << " = 0\n";
}
}
|