Submission #247424

#	Time	Username	Problem	Language	Result	Execution time	Memory
247424		ernestvw	Horses (IOI15_horses)	C++11	54 / 100	144 ms	20732 KiB

horses

#include <bits/stdc++.h>
using namespace std;

using ll = long long;

const ll mod = 1e9 + 7;

int n;
vector<ll> C, P;

ll preprod = 1;

ll fp(ll x, ll y){
	ll res=1;
	while(y){
		if(y%2LL)res*=x;
		res%=mod;
		x*=x;
		x%=mod;
		y/=2LL;
	}
	return res;
}

ll inv(ll x){return fp(x,mod-2LL);}

int solve() {
	ll prod = C[n - 1];
	int best = n - 1;
	long double ldprod = (long double)C[n-1];
	for(int i = n - 2; i >= 0; --i) {
		prod *= C[i];
		ldprod *= C[i];
		long double x = ldprod * (long double)P[best];
		if(x >= 1.5e18) break;
		if(prod * P[best] <= C[i] * P[i]) {
			best = i;
			prod = C[i];
			ldprod = (long double)C[i];
		}
	}
	prod = 1;
	if(n > 1000) {
      	if(best < n - 100) exit(1);
		prod = preprod;
		for(int i = n - 100; i <= best; ++i)
			prod = (prod * C[i]) % mod;
		prod = (prod * P[best]) % mod;
		return int(prod % mod);
	}
	for(int i = 0; i <= best; ++i) {
		prod *= C[i];
		prod %= mod;
	}
	prod *= P[best];
	prod %= mod;
	return int(prod % mod);
}

int init(int N, int X[], int Y[]) {
	n = N;
	C.resize(n);
	P.resize(n);
	for(int i = 0; i < n; ++i) C[i] = X[i];
	for(int i = 0; i < n; ++i) P[i] = Y[i];
	if(n > 1000) {
		preprod = 1;
		for(int i = 0; i < n - 100; ++i) {
			preprod *= C[i];
			preprod %= mod;
		}
	}
	return solve();
}

int updateX(int pos, int val) {
	if(n > 1000 && pos < n - 100) {
		preprod *= inv(C[pos]);
		preprod %= mod;
		preprod *= (ll)val;
		preprod %= mod;
	}
	C[pos] = val;
	return solve();
}

int updateY(int pos, int val) {
	P[pos] = val;
	return solve();
}

• Subtask 1: 17 / 17
• Subtask 2: 17 / 17
• Subtask 3: 20 / 20
• Subtask 4: 0 / 23
• Subtask 5: 0 / 23