Submission #250921

#	Time	Username	Problem	Language	Result	Execution time	Memory
250921		willi19	Split the sequence (APIO14_sequence)	C++14	100 / 100	1483 ms	87416 KiB

sequence

#include <bits/stdc++.h>
using namespace std;
typedef pair<long long,int> pll;
long long s[100100],dp[100100][2];
int n,k,rev[100100][210];
class line
{
    public:
        long long a,b;
    bool operator == (const line& rhs) const
    {
        return (a==rhs.a)&&(b==rhs.b);
    }
};
double cross(line l1, line l2)
{
    return (double) (l1.b-l2.b)/(l2.a-l1.a);
}
class convexhulltrick
{
    public:
        int s,e,ind[100100];
        line deq[100100];
        void insert(line l,int in)
        {
            if(deq[e-1]==l)
            {
                ind[e-1] = in;
                return;
            }
            ind[e] = in;
            deq[e] = l;
            while(s+1<e&&cross(deq[e-2],deq[e-1])>=cross(deq[e-1],deq[e]))
            {
                deq[e-1] = deq[e];
                ind[e-1] = ind[e];
                e--;
            }
            e++;
        }
        pll query(long long x)
        {
            long long l = s,r = e-1;
            while(l!=r)
            {
                long long m = (l+r)/2;
                if(cross(deq[m],deq[m+1])<=x)
                    l = m+1;
                else r = m;
            }
            return {deq[l].a*x+deq[l].b,ind[l]};
        }
    void init()
    {
        s=e=0;
    }
};
convexhulltrick cht;
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    cin>>n>>k;
    for(int i=1;i<=n;i++)
        cin>>s[i];
    for(int i=1;i<=n;i++)
        s[i] += s[i-1];
    for(int i=0;i<k;i++)
    {
        cht.init();
        int ind = (i+1)%2;
        dp[0][ind] = -1000000000000;
        line tmp;
        tmp.a = 0;
        tmp.b = -1000000000000;
        cht.insert(tmp,0);
        for(int j=1;j<=n;j++)
        {
            pll hamin = cht.query(s[j]);
            dp[j][ind] = hamin.first;
            rev[j][i] = hamin.second;
            line tmp;
            tmp.a = s[j];
            tmp.b = dp[j][1-ind]-s[j]*s[j];
            cht.insert(tmp,j);
        }
    }
    long long last = n;
    cout<<dp[n][k%2]<<"\n";
    for(int i=0;i<k;i++)
    {
        last = rev[last][k-i-1];
        cout<<last<<" ";
    }
}

Compilation message (stderr)

sequence.cpp: In function 'int main()':
sequence.cpp:26:23: warning: array subscript is below array bounds [-Warray-bounds]
             if(deq[e-1]==l)
                ~~~~~~~^
sequence.cpp:26:23: warning: array subscript is below array bounds [-Warray-bounds]

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