Submission #223021

#	Time	Username	Problem	Language	Result	Execution time	Memory
223021		emil_physmath	Horses (IOI15_horses)	C++17	17 / 100	823 ms	43384 KiB

horses

#include "horses.h"
#include <limits>
#include <vector>
#include <set>
using namespace std;
using llong = long long;
const llong mod = 1000'000'007;
#define ROOT 1, 0, n - 1
llong Pow(llong a, llong p)
{
    if (p == 0) return 1;
    if (p % 2) return (a * Pow(a, p - 1)) % mod;
    return Pow((a * a) % mod, p / 2);
}
inline llong Inv(llong a) { return Pow(a % mod, mod - 2); }

int n;
vector<int> x, c;
set<int> chng;
llong xmult;

int t[4 * 500'000];
void Set(int v, int vl, int vr, int i, int val)
{
    if (vl == vr)
    {
        t[v] = val;
        return;
    }
    int vm = (vl + vr) / 2;
    if (i <= vm) Set(v * 2, vl, vm, i, val);
    else Set(v * 2 + 1, vm + 1, vr, i, val);
    t[v] = max(t[v * 2], t[v * 2 + 1]);
}
int Max(int v, int vl, int vr, int l, int r)
{
    if (l > vr || vl > r)
        return numeric_limits<int>::min();
    if (l <= vl && vr <= r)
        return t[v];
    int vm = (vl + vr) / 2;
    return max(Max(v * 2, vl, vm, l, r), Max(v * 2 + 1, vm + 1, vr, l, r));
}

struct Rat
{
    llong a, b;
};
inline bool operator<(Rat l, Rat r) { return l.a * r.b < r.a * l.b; }
int Solve()
{
    if (chng.empty())
        return Max(ROOT, 0, n - 1);
    Rat mx{0, 1};
    llong curxmult = 1;
    for (auto it = chng.rbegin(); it != chng.rend() && curxmult < 1000'000'000LL; ++it)
    {
        int i = *it;
        int j = (it == chng.rbegin() ? n : *prev(it));
        mx = max(mx, Rat{Max(ROOT, i, j - 1), curxmult});
        curxmult *= x[i];
    }
    llong res = (mx.a * Inv(mx.b)) % mod;
    return res = (res * xmult) % mod;
}

int init(int N, int X[], int Y[]) {
    n = N;
    x.assign(X, X + N);
    c.assign(Y, Y + N);
    chng.clear();
    for (int i = 0; i < n; ++i)
        Set(ROOT, i, c[i]);
    xmult = 1;
    for (int i = 0; i < n; ++i)
        if (x[i] > 1)
        {
            chng.insert(i);
            xmult = (xmult * x[i]) % mod;
        }
    return Solve();
}

int updateX(int pos, int val) {
    if (x[pos] > 1 && val == 1)
        chng.erase(pos);
    if (x[pos] == 1 && val > 1)
        chng.insert(pos);
    return Solve();
}

int updateY(int pos, int val) {
    Set(ROOT, pos, val);
	return Solve();
}

Compilation message (stderr)

horses.cpp: In function 'int Solve()':
horses.cpp:64:16: warning: conversion to 'int' from 'llong {aka long long int}' may alter its value [-Wconversion]
     return res = (res * xmult) % mod;
            ~~~~^~~~~~~~~~~~~~~~~~~~~

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