Submission #45973

#	Time	Username	Problem	Language	Result	Execution time	Memory
45973		RezwanArefin01	Aliens (IOI16_aliens)	C++17	60 / 100	1016 ms	383076 KiB

aliens

#include <bits/stdc++.h>
#include "aliens.h"
using namespace std;

typedef long long ll; 
typedef pair<int, int> ii;

#define sq(a) ((ll)(a) * (a))
#define cost(j, i) (sq(r[i] - l[j + 1] + 1) - sq(max(0, r[j] - l[j + 1] + 1)))

struct cht {
	vector<ll> m, b; int ptr = 0;
	bool bad(int l1, int l2, int l3) {
		return 1.0 * (b[l3] - b[l1]) * (m[l1] - m[l2]) <= 1.0 * (b[l2] - b[l1]) * (m[l1] - m[l3]);
	}
	void add(ll _m, ll _b) {
		m.push_back(_m); b.push_back(_b); 
		int s = m.size(); 
		while(s >= 3 && bad(s - 3, s - 2, s - 1)) {
			m.erase(m.end() - 2); 
			b.erase(b.end() - 2); 
			s--;
		}
	}
	ll f(int i, ll x) { return m[i] * x + b[i]; }
	ll query(ll x) {
		if(ptr >= m.size()) ptr = m.size() - 1; 
		while(ptr < m.size() - 1 && 
			f(ptr, x) > f(ptr + 1, x)) ptr++;
		return f(ptr, x);
	}
	void clear() { m.clear(), b.clear(), ptr = 0; }
} ds;
ll take_photos(int n, int m, int K, vector<int> R, vector<int> C) {
	vector<ii> tmp; 
	for(int i = 0; i < n; i++) {
		if(R[i] > C[i]) swap(R[i], C[i]); 
		tmp.emplace_back(C[i], R[i]);
	}
	sort(tmp.begin(), tmp.end());
	tmp.erase(unique(tmp.begin(), tmp.end()), tmp.end());
	vector<int> l = {-1}, r = {-1};
	for(ii seg : tmp) {
		if(seg.first == r.back()) continue; 
		while(l.size() && seg.second <= l.back() && r.back() <= seg.first) 
			r.pop_back(), l.pop_back();
		l.push_back(seg.second); 
		r.push_back(seg.first);
	}	

	n = l.size() - 1; 
	ll dp[K + 1][n + 1]; 
	memset(dp, 63, sizeof dp); 

	for(int i = 1; i <= n; i++) 
		dp[1][i] = sq(r[i] - l[1] + 1); 

	for(int k = 2; k <= K; k++) {
		ds.clear();
		ds.add(-2ll * l[1 + 1], dp[k - 1][1] + sq(l[1 + 1]) - sq(max(0, r[1] - l[1 + 1] + 1)));
		for(int i = 2; i <= n; i++) {
			ll x = r[i] + 1; 
			dp[k][i] = ds.query(x) + sq(x);
			if(i < n) ds.add(-2ll * l[i + 1], dp[k - 1][i] + sq(l[i + 1]) - sq(max(0, r[i] - l[i + 1] + 1)));
		} 

	}

	ll ret = 1e18;
	for(int i = 1; i <= K; i++) ret = min(ret, dp[i][n]); 
	return ret;
}

#ifdef LOCAL_TESTING
int main() {
	freopen("in", "r", stdin);
    int n, m, k;
    assert(3 == scanf("%d %d %d", &n, &m, &k));
    std::vector<int> r(n), c(n);
    for (int i = 0; i < n; i++) {
        assert(2 == scanf("%d %d", &r[i], &c[i]));
    }
    ll ans = take_photos(n, m, k, r, c);
    
    printf("%lld\n", ans);
    return 0;
}
#endif

Compilation message (stderr)

aliens.cpp: In member function 'll cht::query(ll)':
aliens.cpp:27:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(ptr >= m.size()) ptr = m.size() - 1; 
      ~~~~^~~~~~~~~~~
aliens.cpp:28:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while(ptr < m.size() - 1 && 
         ~~~~^~~~~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 12 / 12
• Subtask 3: 9 / 9
• Subtask 4: 16 / 16
• Subtask 5: 19 / 19
• Subtask 6: 0 / 40