Submission #6645346

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Source Code Expand

#include<cstdio>
#include<vector>
#include<algorithm>
#include<complex>
using namespace std;
typedef complex<double> C;
typedef long long ll;

typedef vector<C> VC;

VC dft(VC a, ll n, ll sgn = 1) {
  if (n == 1) return a;
  n /= 2;
  VC f(n), g(n);
  for (ll i = 0; i < n; i++) f[i] = a[2*i], g[i] = a[2*i+1];

  f = dft(f, n, sgn);
  g = dft(g, n, sgn);

  C zeta(cos(M_PI/n), sin(M_PI/n) * sgn), pow_zeta = 1;

  for (ll i = 0; i < 2*n; i++) {
    a[i] = f[i%n] + pow_zeta * g[i%n];
    pow_zeta *= zeta;
  }
  return a;
}

VC inv_dft(VC a, ll n) {
  a = dft(a, n, -1);
  for (ll i = 0; i < n; i++) a[i] /= n;
  return a;
}

VC multiply(VC a, VC b) {
  ll sz = a.size() + b.size() + 1, n = 1;
  while (n < sz) n *= 2;
  a.resize(n), b.resize(n);
  a = dft(a, n);
  b = dft(b, n);

  VC f(n);
  for (ll i = 0; i < n; i++) f[i] = a[i] * b[i];
  return inv_dft(f, n);
}


int main() {
  ll n, t1, t2;
  scanf("%lld", &n);
  VC a(n+1), b(n+1);
  for (ll i = 1; i <= n; i++) scanf("%lld%lld", &t1, &t2), a[i] = C(t1), b[i] = (t2);
  VC ans = multiply(a, b);
  for (ll i = 1; i <= 2*n; i++) printf("%lld\n", (ll)(ans[i].real() + 0.5));
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:50:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld", &n);
                    ^
./Main.cpp:52:85: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   for (ll i = 1; i <= n; i++) scanf("%lld%lld", &t1, &t2), a[i] = C(t1), b[i] = (t2);
                                                                                     ^

Judge Result