Submission #33942

#	Time	Username	Problem	Language	Result	Execution time	Memory
33942		petil	Split the sequence (APIO14_sequence)	C++14	71 / 100	2000 ms	85612 KiB

sequence

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
struct CHT{
    ll s[100005], t[100005];
    int id[100005];
    int st, ed, sz;
    CHT(){
        st=0, ed=-1, sz=0;
    }
    bool ck(ll L1s, ll L1t, ll L2s, ll L2t, ll mes, ll met){
        ///x1 =   (L1.t-L2.t) /(L2.s-L1.s)
        ///x2 =   (L2.t - me.t) / (me.s-L2.s)
        ///x1<x2
        return (L1t-L2t) * (mes-L2s) < (L2t-met) * (L2s-L1s) ;
    }
    void init(){
        st=0, ed=-1, sz=0;
    }
    void push(ll ss, ll tt, int idx){

        while(sz>=2 && !ck(s[ed-1], t[ed-1], s[ed], t[ed], ss, tt)){
            --ed;--sz;
        }
        if(sz!=0 && s[ed] == ss){
            if(t[ed]>=tt)return;
            s[ed] = ss;t[ed] = tt;id[ed] = idx;
        }
        else{
            ++sz;++ed;
            s[ed] = ss; t[ed] = tt; id[ed] = idx;
        }
    }
    ll val(int ii, ll x)
    {
        return s[ii] * x + t[ii];
    }
    void Efront(ll x)
    {
        while(sz>=2 && !(val(st, x)>val(st+1, x))){
          //  if(que[1].idx == id)return;
            --sz;++st;
        }
    }
    ll maxval(ll x){
        return val(st, x);
    }

}cht;

int n, k, A[100005];
ll s[100005], dp[100005][2];
int pre[100003][202];
void trace(int now, int j)
{
    vector<int> tmp;
    while(1){
        if(j==0)break;
        tmp.push_back(now);
        now = pre[now][j];--j;
    }
    for(int i=(int)tmp.size()-1; i>=0; i--)
        printf("%d ", tmp[i]);
}

int main()
{
    scanf("%d %d", &n, &k);
    for(int i=1; i<=n; i++){
        scanf("%d", &A[i]);
    }
   for(int i=1; i<=n; i++){
        s[i] = s[i-1] + A[i];
   }


    for(int j=1; j<=k; j++){
        cht.init();
        int pos = 0;
        int t = (j&1);
        for(int i=j; i<=n; i++){
         ///    cht.Efront(s[i]);
            cht.push(s[i-1], -s[i-1]*s[n] + dp[i-1][!t], i-1);
            cht.Efront(s[i]);
            dp[i][t] = cht.maxval(s[i]) + s[i]*(s[n]-s[i]);
            pre[i][j] = cht.id[cht.st];
        }

    }
    ll ans=-1, ed=-1;
    for(int i=k; i<=n; i++){
        if(ans<dp[i][k&1]){
            ans = dp[i][k&1];ed=i;
        }
    }

    cout<<ans<<endl;

    trace(ed, k);
}

Compilation message (stderr)

sequence.cpp: In function 'int main()':
sequence.cpp:79:13: warning: unused variable 'pos' [-Wunused-variable]
         int pos = 0;
             ^
sequence.cpp:68:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &n, &k);
                           ^
sequence.cpp:70:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d", &A[i]);
                           ^

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