Submission #287997

#	Time	Username	Problem	Language	Result	Execution time	Memory
287997		Plurm	Discharging (NOI20_discharging)	C++11	11 / 100	180 ms	5916 KiB

Discharging

#include <bits/stdc++.h>
using namespace std;
int n;
int h[1000005];
set<int> active;
class state{
public:
	int i, j; // join(i,j); (i < j)
	long long diff;
	state(int x, int y, long long d) : i(x), j(y), diff(d) {}
	friend bool operator<(const state& x, const state& y){
		return x.diff > y.diff;
	}
};
long long computeDiff(int i, int j){
	assert(i < j);
	return -1ll*(n-j+1)*h[j] -1ll*(n-i+1)*h[i] + 1ll*(n-i+1)*h[j];
}
bool verifyDiff(state cur){
	int i = cur.i;
	int j = cur.j;
	long long diff = cur.diff;
	return active.count(i) && active.count(j) && computeDiff(i,j) == diff;
}
int main(){
	scanf("%d",&n);
	long long ans = 0ll;
	int mx = 0;
	vector<int> pivots;
	for(int i = 1; i <= n; i++){
		scanf("%d",h+i);
		if(h[i] > mx){
			mx = h[i];
			pivots.push_back(i);
			ans += 1ll * mx * (n-i+1);
		}
	}
	priority_queue<state> pq;
	for(int i = 0; i < pivots.size()-1; i++){
		int idx = pivots[i];
		int nidx = pivots[i+1];
		long long diff = computeDiff(idx, nidx);
		pq.emplace(idx, nidx, diff);
		active.insert(idx);
	}
	active.insert(pivots.back());
	long long out = ans;
	while(!pq.empty()){
		state cur = pq.top();
		pq.pop();
		if(!verifyDiff(cur)) continue;
		ans += cur.diff;
		out = max(out, ans);
		h[cur.i] = h[cur.j];
		active.erase(cur.j);
		auto it = active.upper_bound(cur.j);
		if(it != active.end()){
			int nxtj = *it;
			long long diff = computeDiff(cur.i, nxtj);
			pq.emplace(cur.i, nxtj, diff);
		}
		it = active.lower_bound(cur.i);
		if(it != active.begin()){
			--it;
			int prej = *it;
			long long diff = computeDiff(prej, cur.i);
			pq.emplace(prej, cur.i, diff);
		}
	}
	printf("%lld\n", out);
	return 0;
}

Compilation message (stderr)

Discharging.cpp: In function 'int main()':
Discharging.cpp:39:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |  for(int i = 0; i < pivots.size()-1; i++){
      |                 ~~^~~~~~~~~~~~~~~~~
Discharging.cpp:26:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   26 |  scanf("%d",&n);
      |  ~~~~~^~~~~~~~~
Discharging.cpp:31:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   31 |   scanf("%d",h+i);
      |   ~~~~~^~~~~~~~~~

• Subtask 1: 0 / 9
• Subtask 2: 0 / 13
• Subtask 3: 0 / 25
• Subtask 4: 11 / 11
• Subtask 5: 0 / 14
• Subtask 6: 0 / 28