Submission #37194740

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Source Code Expand

#include <bits/stdc++.h>
#include <atcoder/modint>
#include <atcoder/convolution>
const int MOD=998244353;
using mint = atcoder::static_modint<MOD>;
using namespace std;

typedef long long ll;
#define rep(i,a,n) for (ll i=a;i<(ll)n;i++)

ll read(){ll r;scanf("%lld",&r);return r;}

int n;
mint ans=0;

template<class T>
vector<T>vec(const vector<T>a,int l,int r){ return vector<T>(a.begin()+l,a.begin()+r); }

// g 表示 f(x)(1+a_2 x)...(1+a_{l-1} x), 中[l..r) 的系数 主要用来 取 ai
// 返回 (1+a_l x)(1+a_{l+1} x)...(1+a_{r-1} x), 没有f(x)
vector<mint> dc(int l,int r,const vector<mint>& g){ // dc [l,r) 返回的幂次 肯定是 r-l
  if(l==n) ans=g[0];
  if(r-l==1) return {1,g[0]};
  int m = (l+r)/2;
  auto glm=vec(g,0,m-l); // g[0..m-l) = g[l..m)
  auto dclm = dc(l,m,glm);
  auto gmr = vec(convolution(g,dclm),m-l,r-l); // (g*dclm)[m-l..r-l) = g[m..r)
  return convolution(dclm,dc(m,r,gmr));
}

int main(){
  n=read();
  mint a=read();
  if(n==1){
    printf("%d\n",a.val());
    return 0;
  }
  mint coef=1;
  vector<mint> f={coef};
  rep(i,1,n+1) f.push_back(coef=(coef*(a-i+1)/i));
  dc(2,n+1,vec(f,2,n+1));
  printf("%d\n",ans.val());
  return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘ll read()’:
./Main.cpp:11:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   11 | ll read(){ll r;scanf("%lld",&r);return r;}
      |                ~~~~~^~~~~~~~~~~

Judge Result