Submission #2205898

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Source Code Expand

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <numeric>
#include <functional>
using namespace std;

#define Rep(b, e, i) for(int i = b; i <= e; i++)
#define rep(n, i) Rep(0, n-1, i)

const int MAX = 200000;
const double PI = 3.14159265358979323846;
const double EPS = 1e-12;
const int INF = 1<<31-1;
const int MOD = 1000000007;

typedef long long ll;
typedef pair<ll, ll> llP;
typedef pair<int, int> intP;
typedef std::priority_queue<int> IntPrioQueue; //Z->A
typedef std::priority_queue<int, std::vector<int>, std::greater<int> > IntReversePrioQueue; //A->Z

ll fac[MAX+1],facInv[MAX+1];

ll power(ll e, ll x){ //e^x % MOD
    if (x == 0) return 1LL;
    if (x % 2 != 0) return ((power(e, x-1) * e) % MOD);
    ll temp = power(e, x / 2);
    return (temp * temp) % MOD;
}

ll nck(ll n, ll k){
    if (!(n >= k && k >= 0)) return 0;
    ll temp = (fac[n] * facInv[n-k]) % MOD;
    return ((temp * facInv[k]) % MOD);
}

void fact(void){
    //階乗とその逆元
    fac[0] = facInv[0] = 1; //0! = 1
    //(x!)^(-1) ≡ (x!)^(p-2) (mod p)
    Rep(1, MAX, i) fac[i] = (fac[i-1] * i) % MOD;
    facInv[MAX] = power(fac[MAX], MOD-2);
    Rep(1, MAX-1, i) facInv[MAX-i] = (facInv[MAX-i+1] * (MAX-i+1)) % MOD;
}

void solve(void){
    int N;
    cin >> N;
    int coins[N];
    rep(N, i) scanf("%d\n", &coins[i]);
    // 99points solution
    /*
    vector <int> w(N);
    rep(N, i) w[i] = i;
    double tails = 0;
    do {
        rep(N, i) {
            int c = 0;
            rep(i, j) if (coins[w[i]]%coins[w[j]]==0) c++;
            if (c%2==0) tails++;
        }
    } while(next_permutation(w.begin(), w.end()));
    fact();
    printf("%.6lf\n", tails/fac[N]);
    */
    double ans = 0;
    rep(N, i){
        int factrials = 0;
        rep(N, j){
            if (coins[i]%coins[j]==0) factrials++;
        }
        if (factrials%2==0) ans += 0.5;
        else ans += ((factrials+1) / 2.0) / factrials;
    }
    printf("%.6lf\n", ans);
}

int main(void){
  solve();
  return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘void solve()’:
./Main.cpp:60:39: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     rep(N, i) scanf("%d\n", &coins[i]);
                                       ^

Judge Result