Submission #246505

#	Time	Username	Problem	Language	Result	Execution time	Memory
246505		BartolM	Aliens (IOI16_aliens)	C++17	100 / 100	166 ms	9804 KiB

aliens

#include "aliens.h"
#include <bits/stdc++.h>

using namespace std;

#define pb push_back
#define X first
#define Y second
#define mp make_pair
typedef pair <int, int> pii;
typedef long long ll;
typedef pair <ll, ll> pll;
typedef pair <pll, int> ppi;
typedef pair <ll, int> pli;

const int N=1e5+5;
const int INF=0x3f3f3f3f;
const ll MAX=(ll)INF*INF;
const int K=4005;

vector <pii> v, vec;
vector <ppi> hull;
int ind;
int cnt[N]; ll dp[N];

ll ccw(pll a, pll b, pll c) {
    return a.X*(b.Y-c.Y)+b.X*(c.Y-a.Y)+c.X*(a.Y-b.Y);
}

int cmp1(pii a, pii b) {
    if (a.X==b.X) return a.Y>b.Y;
    return a.X<b.X;
}

ll f(pll a, ll x) {
    return a.X*x+a.Y;
}

pli bin(ll x) {
    if (hull.empty()) return mp(MAX, 0);
    while (ind<(int)hull.size()-1 && f(hull[ind].X, x)>f(hull[ind+1].X, x)) ++ind;
    return mp(f(hull[ind].X, x), hull[ind].Y+1);
}

void dodaj(ppi pp) {
    while (hull.size()>1 && ccw(hull[(int)hull.size()-2].X, hull.back().X, pp.X)<0) {
        hull.pop_back();
    }
    hull.pb(pp);
    if (ind>=hull.size()) ind=(int)hull.size()-1;
}

void solve(ll lambda, int n) {
    ind=0;
    cnt[0]=0;
    hull.clear();
    hull.pb(mp(mp(2*v[1].X, (ll)v[1].X*v[1].X), 0));
    for (int i=1; i<=n; ++i) {
        ll ri=-v[i].Y-1;
        pli curr=bin(ri); curr.X+=ri*ri+lambda;
        cnt[i]=curr.Y; dp[i]=curr.X;
        ll pres=0;
        if (i!=n) pres=max(pres, (ll)(v[i].Y-v[i+1].X+1));
        if (i!=n) dodaj(mp(mp(2*v[i+1].X, curr.X-pres*pres+(ll)v[i+1].X*v[i+1].X), curr.Y));
    }

}

long long take_photos(int n, int m, int k, vector<int> rr, vector<int> cc) {
//    printf("%lld\n", MAX);
    for (int i=0; i<n; ++i) {
        if (rr[i]>cc[i]) swap(rr[i], cc[i]);
        vec.pb(mp(rr[i], cc[i]));
    }
    sort(vec.begin(), vec.end(), cmp1);
    int maxi=-1;
    ll mm=-1;
    for (int i=0; i<n; ++i) {
        if (maxi>=vec[i].Y) continue;
        maxi=vec[i].Y;
        v.pb(vec[i]);
        mm=max(mm, (ll)vec[i].Y); mm=max(mm, (ll)vec[i].X);
//        printf("dodajem [%d %d]\n", vec[i].X, vec[i].Y);
    }
    n=v.size();
    v.insert(v.begin(), mp(-1, -1));
    ll lo=0, hi=(ll)m*m, mid, br=0;

    while (lo<hi) {
        mid=(lo+hi)/2;
        solve(mid, n);
        if (cnt[n]>k) lo=mid+1;
        else hi=mid;
    }
    solve(lo, n);
    return dp[n]-lo*k;
}

Compilation message (stderr)

aliens.cpp: In function 'void dodaj(ppi)':
aliens.cpp:50:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if (ind>=hull.size()) ind=(int)hull.size()-1;
         ~~~^~~~~~~~~~~~~
aliens.cpp: In function 'long long int take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:87:31: warning: unused variable 'br' [-Wunused-variable]
     ll lo=0, hi=(ll)m*m, mid, br=0;
                               ^~

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