Submission #70874

#	Time	Username	Problem	Language	Result	Execution time	Memory
70874		aquablitz11	Aliens (IOI16_aliens)	C++14	4 / 100	3 ms	744 KiB

aliens

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

using ll = long long;
using pli = pair<ll, int>;
using pii = pair<int, int>;
#define F first
#define S second

struct CHT {
    struct line {
        ll m, c;
        int cnt;
        line(ll m, ll c, int cnt) : m(m), c(c), cnt(cnt) {}
        ll get(ll x) { return m*x + c; }
    };
    bool bad(line l1, line l2, line l3) {
        return (l3.c-l1.c)*(l1.m-l2.m) <= (l2.c-l1.c)*(l1.m-l3.m);
    }
    vector<line> f;
    int idx;
    void update(ll m, ll c, int cnt) {
        line l(m, c, cnt);
        while (f.size() > 1 && bad(f[f.size()-2], f[f.size()-1], l))
            f.pop_back();
        f.push_back(l);
    }
    pli query(ll x) {
        idx = min(idx, (int)f.size()-1);
        while (idx < f.size()-1 && f[idx].get(x) >= f[idx+1].get(x))
            ++idx;
        return pli(f[idx].get(x), f[idx].cnt);
    }
    void clear() {
        f.clear();
        idx = 0;
    }
} cht;

int n;
vector<pii> A;
void compress()
{
    sort(A.begin(), A.end(), [&] (pii a, pii b) {
        return pii(a.F, -a.S) < pii(b.F, -b.S);
    });
    vector<pii> ret;
    int en = -1;
    for (auto x : A) if (x.S > en)
        ret.push_back(x), en = x.S;
    A = ret;
    n = A.size();
    A.insert(A.begin(), pii(-1e7, -1e7));
}

inline ll sq(ll x) { return x*x; }
pli solve(ll C)
{
    vector<pli> dp(n+1);
    cht.clear();
    dp[0] = pli(0, 0);
    for (int i = 1; i <= n; ++i) {
        cht.update(-2*A[i].F+2, sq(A[i].F-1)+dp[i-1].F-sq(max(0, A[i-1].S-A[i].F+1)), dp[i-1].S);
        pli q = cht.query(A[i].S);
        dp[i] = pli(q.F + sq(A[i].S) + C, q.S+1);
    }
    return dp[n];
}

long long take_photos(int n, int m, int k, vector<int> r, vector<int> c)
{
    for (int i = 0; i < n; ++i)
        A.push_back(minmax(r[i], c[i]));
    compress();

    ll b = 0, e = sq(m);
    while (b < e) {
        ll v = (b+e)/2;
        if (solve(v).S <= k) e = v;
        else b = v+1;
    }
    return solve(b).F - b*k;
}

Compilation message (stderr)

aliens.cpp: In member function 'pli CHT::query(ll)':
aliens.cpp:31:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         while (idx < f.size()-1 && f[idx].get(x) >= f[idx+1].get(x))
                ~~~~^~~~~~~~~~~~

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