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  -2

  kingofgame    12:25 a.m. 29 Tháng 5, 2024

  include <bits/stdc++.h>

  using namespace std;

  namespace fft {
  typedef double dbl;

  struct num {
      dbl x, y;
      num() { x = y = 0; }
      num(dbl x, dbl y): x(x), y(y) {}
  };
  
  inline num operator+ (num a, num b) { return num(a.x + b.x, a.y + b.y); }
  inline num operator- (num a, num b) { return num(a.x - b.x, a.y - b.y); }
  inline num operator* (num a, num b) { return num(a.x * b.x - a.y * b.y, a.x * b.y + a.y * b.x); }
  inline num conj(num a) { return num(a.x, -a.y); }
  
  int base = 1;
  vector<num> roots = { {0, 0}, {1, 0} };
  vector<int> rev = { 0, 1 };
  
  const dbl PI = acosl(-1.0);
  
  void ensure_base(int nbase) {
      if (nbase <= base) return;
  
      rev.resize(1 << nbase);
      for (int i = 0; i < (1 << nbase); i++) {
          rev[i] = (rev[i >> 1] >> 1) + ((i & 1) << (nbase - 1));
      }
      roots.resize(1 << nbase);
  
      while (base < nbase) {
          dbl angle = 2 * PI / (1 << (base + 1));
          for (int i = 1 << (base - 1); i < (1 << base); i++) {
              roots[i << 1] = roots[i];
              dbl angle_i = angle * (2 * i + 1 - (1 << base));
              roots[(i << 1) + 1] = num(cos(angle_i), sin(angle_i));
          }
          base++;
      }
  }
  
  void fft(vector<num>& a, int n = -1) {
      if (n == -1) {
          n = a.size();
      }
      assert((n & (n - 1)) == 0);
      int zeros = __builtin_ctz(n);
      ensure_base(zeros);
      int shift = base - zeros;
      for (int i = 0; i < n; i++) {
          if (i < (rev[i] >> shift)) {
              swap(a[i], a[rev[i] >> shift]);
          }
      }
      for (int k = 1; k < n; k <<= 1) {
          for (int i = 0; i < n; i += 2 * k) {
              for (int j = 0; j < k; j++) {
                  num z = a[i + j + k] * roots[j + k];
                  a[i + j + k] = a[i + j] - z;
                  a[i + j] = a[i + j] + z;
              }
          }
      }
  }
  
  vector<num> fa, fb;
  vector<int> multiply(vector<int>& a, vector<int>& b) {
      int need = a.size() + b.size() - 1;
      int nbase = 0;
      while ((1 << nbase) < need) nbase++;
      ensure_base(nbase);
      int sz = 1 << nbase;
      if (sz > (int)fa.size()) {
          fa.resize(sz);
      }
      for (int i = 0; i < sz; i++) {
          int x = (i < (int)a.size() ? a[i] : 0);
          int y = (i < (int)b.size() ? b[i] : 0);
          fa[i] = num(x, y);
      }
      fft(fa, sz);
      num r(0, -0.25 / sz);
      for (int i = 0; i <= (sz >> 1); i++) {
          int j = (sz - i) & (sz - 1);
          num z = (fa[j] * fa[j] - conj(fa[i] * fa[i])) * r;
          if (i != j) {
              fa[j] = (fa[i] * fa[i] - conj(fa[j] * fa[j])) * r;
          }
          fa[i] = z;
      }
      fft(fa, sz);
      vector<int> res(need);
      for (int i = 0; i < need; i++) {
          res[i] = fa[i].x + 0.5;
      }
      return res;
  }
  
  vector<int> multiply_mod(vector<int>& a, vector<int>& b, int m, int eq = 0) {
      int need = a.size() + b.size() - 1;
      int nbase = 0;
      while ((1 << nbase) < need) nbase++;
      ensure_base(nbase);
      int sz = 1 << nbase;
      if (sz > (int)fa.size()) {
          fa.resize(sz);
      }
      for (int i = 0; i < (int)a.size(); i++) {
          int x = (a[i] % m + m) % m;
          fa[i] = num(x & ((1 << 15) - 1), x >> 15);
      }
      fill(fa.begin() + a.size(), fa.begin() + sz, num{ 0, 0 });
      fft(fa, sz);
      if (sz > (int) fb.size()) {
          fb.resize(sz);
      }
      if (eq) {
          copy(fa.begin(), fa.begin() + sz, fb.begin());
      }
      else {
          for (int i = 0; i < (int)b.size(); i++) {
              int x = (b[i] % m + m) % m;
              fb[i] = num(x & ((1 << 15) - 1), x >> 15);
          }
          fill(fb.begin() + b.size(), fb.begin() + sz, num{ 0, 0 });
          fft(fb, sz);
      }
      dbl ratio = 0.25 / sz;
      num r2(0, -1);
      num r3(ratio, 0);
      num r4(0, -ratio);
      num r5(0, 1);
      for (int i = 0; i <= (sz >> 1); i++) {
          int j = (sz - i) & (sz - 1);
          num a1 = (fa[i] + conj(fa[j]));
          num a2 = (fa[i] - conj(fa[j])) * r2;
          num b1 = (fb[i] + conj(fb[j])) * r3;
          num b2 = (fb[i] - conj(fb[j])) * r4;
          if (i != j) {
              num c1 = (fa[j] + conj(fa[i]));
              num c2 = (fa[j] - conj(fa[i])) * r2;
              num d1 = (fb[j] + conj(fb[i])) * r3;
              num d2 = (fb[j] - conj(fb[i])) * r4;
              fa[i] = c1 * d1 + c2 * d2 * r5;
              fb[i] = c1 * d2 + c2 * d1;
          }
          fa[j] = a1 * b1 + a2 * b2 * r5;
          fb[j] = a1 * b2 + a2 * b1;
      }
      fft(fa, sz);
      fft(fb, sz);
      vector<int> res(need);
      for (int i = 0; i < need; i++) {
          long long aa = fa[i].x + 0.5;
          long long bb = fb[i].x + 0.5;
          long long cc = fa[i].y + 0.5;
          res[i] = (aa + ((bb % m) << 15) + ((cc % m) << 30)) % m;
      }
      return res;
  }
  
  vector<int> square_mod(vector<int>& a, int m) {
      return multiply_mod(a, a, m, 1);
  }
  

  }

  int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  string s;
  cin >> s;
  string t = s;
  reverse(t.begin(), t.end());
  vector<int> a, b;
  for(auto e : s) {
  a.push_back(e - '0');
  }
  for(auto e : t) {
  b.push_back(e - '0');
  }
  auto c = fft::multiply(a, b);
  int n = a.size();
  for(int i = (int)c.size() - n + 1; i < (int)c.size(); i++) {
  cout << c[i] << " ";
  }
  cout << "\n";
  return 0;
  }

• 
  

  -3

  kingofgame    10:28 p.m. 13 Tháng 5, 2024 ← đã chỉnh sửa →

  https://ideone.com/0 sol cho bài này nhé

• 
  

  0

  tk22NguyenMinhPhuc    12:01 p.m. 5 Tháng 11, 2023

  có ai giản bài này cho mình được ko ?
  python nha

  1 phản hồi