| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 1206362 | pera | Horses (IOI15_horses) | C++20 | 0 ms | 0 KiB |
#include<bits/stdc++.h>
#include "horses.h"
#define LL long long
#define int long long
using namespace std;
const int N_MAX = 5E5 + 1;
const LL mod = 1E9 + 7;
int n;
set<int> S;
vector<int> x(N_MAX);
template<typename T>
struct segment_tree{
vector<T> st , a;
T neutral;
int size;
function<T(T , T)> join;
segment_tree(int _size , vector<T> _a , T _neutral , function<T(T , T)> _join){
join = _join;
size = _size;
neutral = _neutral;
a = _a;
st = vector<T>(2 * _size , _neutral);
build();
}
segment_tree(int _size , T _neutral , function<T(T , T)> _join){
join = _join;
size = _size;
neutral = _neutral;
st = vector<T>(2 * _size , _neutral);
}
void build(){
for(int i = 2 * size - 1;i > 0;i --){
st[i] = (i < size ? join(st[i << 1] , st[i << 1 | 1]) : a[i - size + 1]);
}
}
void point_update(int x , T val){
--x;
st[x + size] = join(val , st[x + size]);
for(x += size;x > 1;x >>= 1){
st[x >> 1] = join(st[x] , st[x ^ 1]);
}
}
void point_assign(int x , T val){
--x;
st[x + size] = val;
for(x += size;x > 1;x >>= 1){
st[x >> 1] = join(st[x] , st[x ^ 1]);
}
}
T range_query(int l , int r){
if(l > r){
return neutral;
}
--l;
T resL = neutral , resR = neutral;
for(l += size , r += size;l < r;l >>= 1 , r >>= 1){
if(l & 1){
resL = join(resL , st[l++]);
}
if(r & 1){
resR = join(st[--r] , resR);
}
}
return join(resL , resR);
}
};
int stf(int x , int y){
return max(x , y);
};
LL sff(LL x , LL y){
return x * y % mod;
};
segment_tree<int> st(N_MAX , 0 , stf);
segment_tree<LL> sf(N_MAX , 1 , sff);
int calc(){
if(S.empty()){
return st.range_query(1 , n);
}
LL val = 1;
auto it = --S.end();
vector<int> v;
while(it != S.end()){
val *= x[*it];
if(val > 1E9){
break;
}
v.emplace_back(*it);
if(it == S.begin()){
break;
}
--it;
}
int sz = (int)v.size();
reverse(v.begin() , v.end());
vector<int> vY(sz);
for(int i = 0;i < sz;i ++){
vY[i] = st.range_query(v[i] + 1 , (i == sz - 1 ? n : v[i + 1]));
}
//find suffix maximums
vector<bool> g(sz);
vector<int> t(sz);
t[0] = x[v[0]];
for(int i = 1;i < sz;i ++){
t[i] = t[i - 1] * x[v[i]];
}
LL mx = 0;
for(int i = sz - 1;i >= 0;i --){
if(t[i] * vY[i] > mx){
mx = t[i] * vY[i];
g[i] = true;
}
}
//best ending
LL best = 0 , F = -1 , sum = 0 , prd = 1;
for(int i = 0;i < sz;i ++){
prd *= x[v[i]];
if(g[i]){
if(F != -1){
sum += (prd - 1) * vY[i];
}
if(F == -1){
LL P = sf.range_query(1 , v[i] + 1);
--P;
if(P < 0){
P += mod;
}
F = P * vY[i] % mod;
}
prd = 1;
best = max(best , sum + vY[i]);
}
}
return (F + best) % mod;
}
int init(int N, int X[], int Y[]) {
n = N;
for(int i = 0;i < N;i ++){
x[i] = X[i];
if(X[i] > 1){
S.insert(i);
}
sf.point_assign(i + 1 , X[i]);
st.point_assign(i + 1 , Y[i]);
}
return calc();
}
int updateX(int pos, int val) {
if(x[pos] > 1){
S.erase(pos);
}
x[pos] = val;
if(x[pos] > 1){
S.insert(pos);
}
sf.point_assign(pos + 1, x[pos]);
return calc();
}
int updateY(int pos, int val) {
st.point_assign(pos + 1 , val);
return calc();
}