Submission #170304

#	Time	Username	Problem	Language	Result	Execution time	Memory
170304		dennisstar	Aliens (IOI16_aliens)	C++11	100 / 100	136 ms	9944 KiB

aliens

#include "aliens.h"
#include <bits/stdc++.h>
#define fi first
#define se second
#define ryan bear
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef long double ld;
typedef vector<int> vim;
typedef vector<ll> vlm;
 
int n, m;
 
pii im[100010]; vim chk(100010);
vector<pll> ar;
 
ll sq(ll i) {return i*i;}
pll stk[100010]; ll cnt[100010]; int fr, tp;
 
ll lin(ll i, ll x) { return stk[i].fi*x+stk[i].se;}
pll cal(ll x) {
	while (fr<=tp-2 && lin(fr, x)>=lin(fr+1, x)) fr++;
	return {lin(fr, x), cnt[fr]};
}
 
void add(ll a, ll b, ll c) {
	while (fr<=tp-2 && (stk[tp-1].fi-a)*(stk[tp-1].se-stk[tp-2].se) > (stk[tp-2].fi-stk[tp-1].fi)*(b-stk[tp-1].se)) tp--;
	stk[tp]={a, b};
	cnt[tp]=c;
	tp++;
}
 
pll f(ll cost) {
	fr=tp=0;
 
	vlm Dp(n+1), c(n+1);
	add(-2*(ar[1].se-1), sq(ar[1].se-1)+cost, 1);
	Dp[1]=cal(ar[1].fi).fi+sq(ar[1].fi);
	c[1]=1;
 
	pll pl;
	
	for (int i=2; i<=n; i++) {
		add(-2*(ar[i].se-1), sq(ar[i].se-1)-sq( max(0ll, (ar[i-1].fi-ar[i].se+1)) )+Dp[i-1]+cost, c[i-1]+1);
		pl=cal(ar[i].fi);
		Dp[i]=sq(ar[i].fi)+pl.fi, c[i]=pl.se; 
	}
	return {c[n], Dp[n]-c[n]*cost};
}
 
ll take_photos(int n_, int m_, int k, vim r, vim c) { //(r-c+1)^2
	n=n_; m=m_;
	for (int i=0; i<n; i++) r[i]++, c[i]++;
	for (int i=0; i<n; i++) {if (r[i]<c[i]) swap(r[i], c[i]);}
	for (int i=0; i<n; i++) im[i]={r[i],c[i]};
 
	sort(im, im+n, [](pii pi1, pii pi2){return pi1.fi==pi2.fi?pi1.se<pi2.se:pi1.fi>pi2.fi;});
	int mn=m+1;
	ar.push_back({0,0});
	for (int i=0; i<n; i++) {
		if (mn<=im[i].se) continue;
		ar.push_back({(ll)im[i].fi, (ll)im[i].se});
		mn=min(mn, im[i].se);
	}
	n=ar.size()-1;
	sort(ar.begin(), ar.end());
	ll s=0, e=((ll)m*m);
	ll ret;
	ll x1, x2, y1, y2;
	x1=y1=y2=0; x2=e;
	k=min(k, n);
	while (s<=e) {
		ll md=(s+e)/2;
		pll pl=f(md);
		if (pl.fi==k) return pl.se; 
		else if (pl.fi<k) {
			e=md-1;
			if (x1<pl.fi) x1=pl.fi, y1=pl.se;
		}
		else {
			s=md+1;
			if (x2>pl.fi) x2=pl.fi, y2=pl.se;
		}
	}
	return y2+(y1-y2)/(x2-x1)*(x2-k);
}
		

Compilation message (stderr)

aliens.cpp: In function 'll take_photos(int, int, int, vim, vim)':
aliens.cpp:70:5: warning: unused variable 'ret' [-Wunused-variable]
  ll ret;
     ^~~

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