Submission #34076970

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Source Code Expand

#include <bits/stdc++.h>
#include <atcoder/all>

using namespace std;
using namespace atcoder;

using ll = long long;
typedef pair<double,double> P;
#define SORT(a) sort((a).begin(),(a).end())
#define REV(a) reverse((a).begin(),(a).end())
#define For(i, a, b)    for(ll i = (a) ; i < (b) ; ++i)
#define rep(i, n)       For(i, 0, n)
#define debug(x)  cerr << #x << " = " << (x) << endl;
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }

void coY() {cout <<"Yes"<<endl;}
void coN(){cout <<"No"<<endl;}
void coT() {cout <<"Takahashi"<<endl;}
void coA(){cout <<"Aoki"<<endl;}

void mswap(ll &a, ll &b){ if(a >= b) swap(a,b); }
void rswap(ll &a, ll &b){ if(a <= b) swap(a,b); }

const ll dy[] = {0,0,1,-1};
const ll dx[] = {1,-1,0,0};
const ll mod = 1e9+7;
const ll MOD = 998244353;
using mint = modint998244353;
const double PI=3.14159265358979323846;
const ll inf = 1001001001;
const ll INF = 1'000'000'000'000'000'000;
vector<ll> to[200'005];
//Write From this Line
P dp[200'005];
int main()
{
	int n, m, k;
	cin >> n>> m>> k;
	map<int,bool> mp;
	rep(i,k){
		int x;
		cin >> x;
		mp[x] = true;
	}
	int ren = 0;
	rep(i,n){
		if(mp[i]){
			ren ++;
			if(ren >= m){
				cout << -1 << endl;
				return 0;
			}
		} else {
			ren = 0;
		}
	}
	dp[n] = P(0,0);
	for(int i=n; i<=n+m; i++){
		dp[i] = P(0,0);
	}
	P syaku = P(0,0);
	for(int i = n-1; i >= 0; i--){
		if(mp[i]){
			dp[i] = P(1,0);
		} else {
			dp[i].first = syaku.first/m;
			dp[i].second = 1+(syaku.second/m);
		}
		syaku.first -= dp[i+m].first;
		syaku.second -= dp[i+m].second;
		syaku.first += dp[i].first;
		syaku.second += dp[i].second;
	}
	double ans = dp[0].second / (1-dp[0].first);
	cout << setprecision(15);
	cout << ans << endl;
}

Submission Info

Judge Result