Submission #46538

#	Time	Username	Problem	Language	Result	Execution time	Memory
46538		tieunhi	Split the sequence (APIO14_sequence)	C++14	11 / 100	2086 ms	86944 KiB

sequence

#include <bits/stdc++.h>
#define pii pair<int, int>
#define mp make_pair
#define F first
#define S second
#define PB push_back
#define N 100005
#define maxc 1000000007

using namespace std;

int n, k, a[N], tr[N][202];
long long s[N], dp[N];

struct ConvexHullTrick
{
    vector<long long> U;
    vector<long long> V;
    vector<int> ID;
    int pointer = 0;

    bool bad(int l1, int l2, int l3)
    {
        return (V[l3] - V[l1])*(U[l1] - U[l2]) < (V[l2] - V[l1])*(U[l1] - U[l3]);
    }
    void add(long long u, long long v, int id)
    {
        U.PB(u); V.PB(v); ID.PB(id);
        while (U.size() >= 3 && bad(U.size()-3, U.size()-2, U.size()-1))
        {
            U.erase(U.end()-1);
            V.erase(V.end()-1);
            ID.erase(ID.end()-1);
        }
    }
    long long gett(int pos, long long val)
    {
        return U[pos]*val + V[pos];
    }
    pair<long long, int> get(long long val, int pos)
    {
        if (pointer >= U.size()) pointer = U.size()-1;
        while (pointer < U.size()-1 && gett(pointer, val) <= gett(pointer+1, val) && ID[pointer+1] < pos)
            pointer++;
        return mp(gett(pointer, val), ID[pointer]);
    }
    void xoa()
    {
        U.clear();
        V.clear();
        ID.clear();
    }

}CHT[2];
int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    //freopen("INP.TXT", "r", stdin);
    //freopen("OUT.TXT", "w", stdout);
    cin >> n >> k;
    for (int i = 1; i <= n; i++) cin >> a[i], s[i] = s[i-1] + a[i];

    CHT[0].add(0, 0, 0);
    for (int j = 1; j <= k+1; j++)
    {
        for (int i = j; i <= n; i++)
        {
            pair<long long, int> z = CHT[0].get(2*s[i], i);
            dp[i] = s[n]*s[i] - s[i]*s[i] + z.F;
            tr[i][j] = z.S;
            CHT[1].add(s[i], dp[i] - s[n]*s[i] - s[i]*s[i], i);
        }
        swap(CHT[0], CHT[1]);
        CHT[0].pointer = 0;
        CHT[1].xoa();
    }
    int i = n, j = k+1;
    cout <<dp[n]/2<<'\n';
    vector<int> res;
    while (i != 0)
    {
        res.PB(i);
        i = tr[i][j--];
    }
    reverse(res.begin(), res.end());
    for (int i = 0; i < res.size()-1; i++)
        cout <<res[i]<<" ";
}

Compilation message (stderr)

sequence.cpp: In member function 'std::pair<long long int, int> ConvexHullTrick::get(long long int, int)':
sequence.cpp:42:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if (pointer >= U.size()) pointer = U.size()-1;
             ~~~~~~~~^~~~~~~~~~~
sequence.cpp:43:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         while (pointer < U.size()-1 && gett(pointer, val) <= gett(pointer+1, val) && ID[pointer+1] < pos)
                ~~~~~~~~^~~~~~~~~~~~
sequence.cpp: In function 'int main()':
sequence.cpp:86:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < res.size()-1; i++)
                     ~~^~~~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 0 / 11
• Subtask 3: 0 / 11
• Subtask 4: 0 / 17
• Subtask 5: 0 / 21
• Subtask 6: 0 / 29