Submission #1083223

#	Time	Username	Problem	Language	Result	Execution time	Memory
1083223		kiethm07	Split the sequence (APIO14_sequence)	C++11	100 / 100	609 ms	84648 KiB

sequence

#include <bits/stdc++.h>

#define pii pair<int,int>
#define iii pair<int,pii>
#define fi first
#define se second

#define vi vector<int>
#define vii vector<pii>
#define pb(i) push_back(i)
#define all(x) x.begin(),x.end()

#define TEXT "a"

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

const int inf = 1e9 + 7;
const ld eps = 1e-8;
const double pi = acos(-1);
const int N = 1e5 + 5;
const int K = 205;

int n,k;
ll p[N];
ll dp[N][2];
int pre[N][K];

struct line{
    ll a,b;
    int id;
    line(ll _a, ll _b, int _id){
        a = _a;
        b = _b;
        id = _id;
    }
    ll eval(ll x){
        return a * x + b;
    }
    double isect(const line& F) const{
        return 1.0 * (F.b - b) / (a - F.a);
    }
};

struct CHT{
    deque<line> dq;
    void add(line F){
        int n = dq.size();
        bool f = 1;
        while(n >= 2){
            if (dq.back().a == F.a){
                if (dq.back().b <= F.b){
                    n--;
                    dq.pop_back();
                }
                else f = 0;
                break;
            }
            if (dq[n - 2].isect(dq[n - 1]) < F.isect(dq[n - 1])) break;
            n--;
            dq.pop_back();
        }
        if (n == 1){
            if (dq[0].a == F.a){
                if (dq[0].b <= F.b){
                    n--;
                    dq.pop_back();
                }
                else f = 0;
            }
        }
        if (f) dq.push_back(F);
    }
    pair<ll,int> query(ll x){
        int n = dq.size();
        while(n >= 2 && dq[0].eval(x) <= dq[1].eval(x)){
            n--;
            dq.pop_front();
        }
        return make_pair(dq[0].eval(x),dq[0].id);
    }
};

int main(){
    cin.tie(0) -> sync_with_stdio(0);
    if (fopen(TEXT".inp","r")){
        freopen(TEXT".inp","r",stdin);
        freopen(TEXT".out","w",stdout);
    }
    cin >> n >> k;
    for (int i = 1; i <= n; i++){
        cin >> p[i];
        p[i] += p[i - 1];
    }
    int cur, last;
    for (int used = 1; used <= k; used++){
        cur = used & 1;
        last = cur ^ 1;
        CHT c;
        c.add(line(0,0,0));
        for (int i = 1; i < n; i++){
//            for (int j = 0; j < i; j++){
//                dp[i][used] = max(dp[i][used], dp[j][used - 1] + (p[i] - p[j]) * (p[n] - p[i]));
//                if (dp[i][used] == dp[j][used - 1] + (p[i] - p[j]) * (p[n] - p[i])) pre[i][used] = j;
//            }
            auto tmp = c.query(-(p[n] - p[i]));
            dp[i][cur] = p[i] * (p[n] - p[i]) + tmp.fi;
            pre[i][used] = tmp.se;
            c.add(line(p[i], dp[i][last], i));
        }
    }
    int best = 0;
    for (int i = 1; i < n; i++){
        if (dp[i][cur] >= dp[best][cur]) best = i;
    }
    cout << dp[best][cur] << "\n";
    vector<int> v;
    for (int used = k; used >= 1; used--){
        v.push_back(best);
        best = pre[best][used];
    }
    reverse(all(v));
    for (int i : v){
        if (i == 0) cout << "LMAO\n";
        cout << i << " ";
    }
    return 0;
}

Compilation message (stderr)

sequence.cpp: In function 'int main()':
sequence.cpp:90:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   90 |         freopen(TEXT".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
sequence.cpp:91:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   91 |         freopen(TEXT".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
sequence.cpp:119:25: warning: 'cur' may be used uninitialized in this function [-Wmaybe-uninitialized]
  119 |     cout << dp[best][cur] << "\n";
      |                         ^

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