This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include<bits/stdc++.h>
#define el '\n'
using namespace std ;
mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());
const int64_t inf = 1e18;
const int MN = 5e5 + 5;
int a[MN] , n;
namespace sub_trau{
int x[25] , ans = 0;
void backtrack(int k){
if (k > n - 1){
int cur = 0 , sum = 0 , cnt = 0;
bool check = true;
for ( int i = 1 ; i <= n; i++ ){
sum += a[i];
if (x[i] == 1){
if (sum < cur){
check = false;
break;
}
cnt++;
cur = sum;
sum = 0;
}
}
if (check) ans = max(ans , cnt);
return;
}
for ( int i = 0 ; i <= 1 ; i++ ){
x[k] = i;
backtrack(k + 1);
}
}
void solve(){
x[n] = 1;
backtrack(1);
cout << ans;
}
}
namespace sub2{
void solve(){
vector<int64_t> pref(n + 5);
vector<bool> is_greater(n + 5 , false);
deque<int> dq;
for ( int i = 1 ; i <= n ; i++ ){
while (!dq.empty() && dq.back() <= a[i]) dq.pop_back();
if (dq.size() && dq.front() > a[i]) is_greater[i] = true;
dq.push_back(a[i]);
}
for ( int i = 1 ; i <= n ; i++ ) pref[i] = pref[i - 1] + a[i];
vector<vector<int64_t>> dp(n + 5 , vector<int64_t>(n + 5));
for ( int i = 1 ; i <= n ; i++ ){
for ( int j = i - is_greater[i] ; j >= 1 ; j-- ){
int l = 0 , r = j , pos = -1;
while (l <= r){
int mid = l + r >> 1;
if (pref[j - 1] - pref[mid - 1] <= pref[i] - pref[j - 1]){
pos = mid;
r = mid - 1;
}
else l = mid + 1;
}
assert(pos != -1);
for ( int k = pos ; k <= j - 1 ; k++ ) {
if (is_greater[j - 1] && k == j - 1) continue;
dp[i][j] = max(dp[i][j] , dp[j - 1][k] + 1);
}
}
}
int64_t ans = 0;
for ( int i = 1 ; i <= n ; i++ ){
ans = max(ans , dp[n][i]);
}
cout << ans;
}
}
int32_t main (){
// freopen("segments.inp" , "r" , stdin);
// freopen("segments.out" , "w" , stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n;
for ( int i = 1 ; i <= n ; i++ ) cin >> a[i];
// if (n <= 20){
// sub_trau::solve();
// return 0;
// }
if (n <= 3000){
sub2::solve();
return 0;
}
}
Compilation message (stderr)
segments.cpp: In function 'void sub2::solve()':
segments.cpp:63:23: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
63 | int mid = l + r >> 1;
| ~~^~~
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