Submission #200534

#	Time	Username	Problem	Language	Result	Execution time	Memory
200534		a1_N	Bigger segments (IZhO19_segments)	C++17	37 / 100	1587 ms	148660 KiB

segments

#include <bits/stdc++.h>

#define F first
#define S second

using namespace std;

const int N = 5e5 + 5;
const long long M = (long long)1e15;

int n,a[N];

long long pref[N];

pair<long long,long long> dp[N];

/*
int slow(){
	for(int i = 1; i <= n; i++) pref[i] = pref[i - 1] + a[i];
	dp[1] = {1,a[1]};
	for(int i = 2; i <= n; i++){
		dp[i] = {dp[i - 1].F,dp[i - 1].S + a[i]};
		for(int j = i - 1; j >= 1; j--){
			if(pref[i] - pref[j] >= dp[j].S && dp[i].F <= dp[j].F + 1){
				dp[i] = {dp[j].F + 1,pref[i] - pref[j]};
				break;
			}
		}
	}
	return dp[n].F;
}
*/

unordered_map< long long,pair<long long,long long> > t;

void upd(long long pos,pair<long long,long long> val,long long v = 1,long long tl = 1,long long tr = M){
	if(tl == tr){
		t[v] = val;
		return;
	}	
	long long tm = tl + tr >> 1;
	if(pos <= tm) upd(pos,val,v + v,tl,tm);
	else upd(pos,val,v + v + 1,tm + 1,tr);
	t[v] = max(t[v + v],t[v + v + 1]);
}

pair<long long,long long> get(long long l,long long r,long long v = 1,long long tl = 1,long long tr = M){
	if(l <= tl && tr <= r) return t[v];
	if(tl > r || tr < l) return {0,0};
	long long tm = tl + tr >> 1;
	return max(get(l,r,v + v,tl,tm),get(l,r,v + v + 1,tm + 1,tr));
} 

int fast(){
	for(int i = 1; i <= n; i++) pref[i] = pref[i - 1] + a[i],dp[i] = {0,0};
	dp[1] = {1,a[1]};
	upd(pref[1] + dp[1].S,{dp[1].F,1});
	// update in position pref[i] + dp[i].second -> {dp[i].first,postition}
	for(int i = 2; i <= n; i++){
		dp[i] = {dp[i - 1].F,dp[i - 1].S + a[i]};
		pair<long long,long long> cur = get(1,pref[i]);
		//cerr << cur.F << " " << cur.S << endl;
		if(cur.F > 0) dp[i] = {cur.F + 1,pref[i] - pref[cur.S]};
		upd(pref[i] + dp[i].S,{dp[i].F,i});	
	}
	return dp[n].F;
}

int main(){
	ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	cin >> n;
	for(int i = 1; i <= n; i++) cin >> a[i];
	/*
	cout << "Exact Solution,SLOW " << slow() << endl;
	cout << "Not Exact,FAST " << fast();	
	*/
	cout << fast();
	return 0;
}

Compilation message (stderr)

segments.cpp: In function 'void upd(long long int, std::pair<long long int, long long int>, long long int, long long int, long long int)':
segments.cpp:41:20: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  long long tm = tl + tr >> 1;
                 ~~~^~~~
segments.cpp: In function 'std::pair<long long int, long long int> get(long long int, long long int, long long int, long long int, long long int)':
segments.cpp:50:20: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  long long tm = tl + tr >> 1;
                 ~~~^~~~

• Subtask 1: 13 / 13
• Subtask 2: 14 / 14
• Subtask 3: 10 / 10
• Subtask 4: 0 / 36
• Subtask 5: 0 / 27