Submission #402669

#TimeUsernameProblemLanguageResultExecution timeMemory
402669danielcm585Aliens (IOI16_aliens)C++14
0 / 100
1 ms300 KiB
#include "aliens.h"

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

#define fi first
#define se second

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

const int N = 1e5;
const ll INF = 1e18;
ll dp[N+2], bt[N+2];

struct line {
    ll m, c;

    line(ll x, ll y): m(x), c(y) {}

    ll operator () (ll x) {
        return m*x+c;
    }
};

struct convexHull {
    vector<line> v;
    vector<int> id;

    bool greater(ll a, ll b, ll c, ll d) {
        if (a/b != c/d) return a/b > c/d;
        return (a%b)*d >= (c%d)*b;
    }

    bool bad(line a, line b, line c) {
        return greater(b.c-a.c,a.m-b.m,c.c-b.c,b.m-c.m);
    }

    void insert(line x, int y) {
        int sz = v.size();
        while (sz >= 2 && bad(v[sz-2],v[sz-1],x)) {
            v.pop_back(); sz--;
            id.pop_back();
        }
        v.push_back(x);
        id.push_back(y);
    }

    ii query(ll x) {
        ii ret = ii(INF,0);
        for (int l = 0, r = v.size()-1; l <= r; ) {
            int mid = (l+r)/2;
            if (v[mid](x) < ret.fi || v[mid](x) == ret.fi && bt[id[mid]] < bt[ret.se]) ret = ii(v[mid](x),id[mid]);
            if (mid+1 <= r && v[mid+1](x) < v[mid](x)) l = mid+1;
            else r = mid-1;
        }
        return ret;
    }
};

ll sqr(ll a) {
    return a*a;
}

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.push_back(ii(R[i],C[i]));
    }
    sort(tmp.begin(),tmp.end());
    vector<int> r, c;
    r.push_back(-1); c.push_back(-1);
    for (auto i : tmp) {
        while (!r.empty() && r.back() == i.fi) {
            r.pop_back(); c.pop_back();
        }
        r.push_back(i.fi); c.push_back(i.se);
    }
    n = r.size()-1;
    convexHull ch;
    for (int i = 1; i <= n; i++) {
        if (bt[i-1]+1 <= k) ch.insert(line(-2*(r[i]-1),dp[i-1]+sqr(r[i]-1)),i-1);
        ii opt = ch.query(c[i]);
        dp[i] = opt.fi+sqr(c[i]);
        bt[i] = bt[opt.se]+1;
        // cout << dp[i] << ' ';
    }
    // cout << '\n';
    return dp[n];
}

/*
5 7 2
0 3
4 4
4 6
4 5
4 6

2 6 2
1 4
4 1
*/

Compilation message (stderr)

aliens.cpp: In member function 'ii convexHull::query(ll)':
aliens.cpp:53:59: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   53 |             if (v[mid](x) < ret.fi || v[mid](x) == ret.fi && bt[id[mid]] < bt[ret.se]) ret = ii(v[mid](x),id[mid]);
      |                                       ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
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