Submission #4012506

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Source Code Expand

#include <iostream>
#include <string>
#include <string.h>
#include <algorithm>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <cmath>
#include <stdio.h>
#include <vector>
#include <thread>
#include <atomic>
#include <mutex>
#include <future>
#define int long long
#define endre getchar();getchar();return 0
#define INF 1000000007
#define rep(i,n) for(int i=0;i<n;i++)
#define P pair<int,int>
#define prique(T) priority_queue<T,vector<T>,greater<T>>
#define vecunique(vec) sort(vec.begin(), vec.end());decltype(vec)::iterator result = std::unique(vec.begin(), vec.end());vec.erase(result, vec.end())
using namespace std;
bool prime(int n) {
	for (int i = 2; i <= sqrt(n); i++) {
		if (n%i == 0)return false;
	}
	return n != 1;
}
int gcd(int x, int y) {
	if (x < y)swap(x, y);
	if (y == 0)return x;
	return gcd(y, x%y);
}
int lcm(int x, int y) {
	return x * y / gcd(x, y);
}
int kai(int n) {
	if (n == 0)return 1;
	return (kai(n - 1)*n) % INF;
}
int mod_pow(int x, int y, int mod) {
	int res = 1;
	while (y > 0) {
		if (y & 1) {
			res = res * x%mod;
		}
		x = x * x%mod;
		y >>= 1;
	}
	return res;
}
int mystoi(string s) {
	int cnt = 0;
	for (int i = 0; i < s.size(); i++) {
		cnt += (int)(s[i] - '0') * mod_pow(10, s.size() - i - 1, INF);
	}
	return cnt;
}
/*--------Library Zone!--------*/
int n, c[105], cnt[105];
double ans;
signed main() {
	cin >> n;
	rep(i, n)cin >> c[i];
	rep(i, n) {
		rep(j, n) {
			if (i == j)continue;
			if (c[i] % c[j] == 0)cnt[i]++;
		}
	}
	rep(i, n) {
		if (cnt[i] % 2 == 0) {
			ans += ((double)(cnt[i]) / 2. + 1.) / ((double)(cnt[i]) + 1.);
		}
		else {
			ans += 0.5;
		}
	}
	printf("%.12lf\n", ans);
	endre;
}

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