Submission #34448377

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Source Code Expand

#include <bits/stdc++.h>
const int MOD = 998244353;
typedef long long ll;
#define rep(i,a,n) for (ll i=a;i<(ll)n;i++)

const int N = 1000000;
const int P = N + 10;
bool pr[P]; // 1e6
ll a[2][N+10]; // [0] 1~k 分母, [1] n-k+1 ~ n, 分子

ll read(){ll r;scanf("%lld",&r);return r;} // read
int main(){
  ll n = read();
  ll k = read();
  std::fill(pr+2,pr+P,true);
  for(ll p=2;p*p < P;p++) if(pr[p]) for(ll i = p*p;i < P;i+=p) pr[i]=false;

  ll s[] = {n-k+1,1}; // 最小的数的起始, n-k+1~n 分子部分, 1~k 分母部分
  rep(o,0,2) std::iota(a[o],a[o]+k,s[o]);
  ll ans = 1;
  rep(p,2,P) if(pr[p]){
    int power = 0; // 质因子p的幂次
    rep(o,0,2) for(ll v=((s[o]+(p-1))/p)*p;v<=s[o]+k-1;v+=p) while(a[o][v-s[o]]%p==0){
      power+= (const int[]){1,-1}[o]; // 对幂次影响, 分子+1, 分母-1,
      a[o][v-s[o]] /= p;
    }
    (ans *= power+1) %= MOD;
  }
  rep(i,0,k) (ans *= (1+(a[0][i] != 1)))%=MOD; // > P 的质数因子
  printf("%lld\n",ans);
}

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;} // read
      |                ~~~~~^~~~~~~~~~~

Judge Result