Submission #869330

#	Time	Username	Problem	Language	Result	Execution time	Memory
869330		prohacker	Split the sequence (APIO14_sequence)	C++14	0 / 100	25 ms	131072 KiB

sequence

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define int long long

using namespace std;

const int N = 1e5+10;
const int INF = INT_MAX;
const int mod = 1e9+7;

int n,m;
ll dp[N][205],ans;
int s[N],trace[N][205];
stack<int> st;
int pointer;
vector<ll> M;
vector<ll> B;
vector<int> idx;

bool bad(int l1,int l2,int l3) {
    return (ld)(B[l3]-B[l1])/(B[l2]-B[l1]) < (ld)(M[l1]-M[l3])/(M[l1]-M[l2]);
}

void add(ll m,ll b, int id) {
    M.push_back(m);
    B.push_back(b);
    idx.push_back(id);
    while(M.size() >= 3 and bad(M.size()-3,M.size()-2,M.size()-1)) {
        M.erase(M.end()-2);
        B.erase(B.end()-2);
        idx.erase(idx.end()-2);
    }
}

pair<ll,int> query(ll x) {
    if (pointer >= M.size()) {
        pointer = M.size()-1;
    }
    while(pointer < M.size()-1 and 1LL*M[pointer+1]*x+B[pointer+1] > 1LL*M[pointer]*x+B[pointer]) {
        pointer++;
    }
    return {1LL*M[pointer]*x+B[pointer],idx[pointer]};
}

signed main()
{
    if (fopen("task.inp", "r")) {
        freopen("task.inp", "r", stdin);
        freopen("task.out", "w", stdout);
    }
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    for(int i = 1 ; i <= n ; i++) {
        int x; cin >> x;
        s[i] = s[i-1] + x;
    }
    for(int k = 1 ; k <= m ; k++) {
        for(int i = 1 ; i <= n ; i++) {
            add(s[i-1],dp[i-1][k-1]-1LL*s[i-1]*s[n],i-1);
            pair<ll,int> val = query(s[i]);
            dp[i][k] = val.first+1LL*s[i]*(s[n]-s[i]);
            trace[i][k] = val.second;
//            for(int j = i-1 ; j >= 0 ; j--) {
//                if(dp[j][k-1]+1LL*(s[i]-s[j])*(s[n]-s[i]) > dp[i][k]) {
//                    dp[i][k] = dp[j][k-1]+1LL*(s[i]-s[j])*(s[n]-s[i]);
//                    trace[i][k] = j;
//                }
//            }
        }
        B.clear();
        M.clear();
        idx.clear();
        pointer = 0;
    }
    int id;
    ans = -1;
    for(int i = 1 ; i <= n ; i++) {
        if(dp[i][m] > ans) {
            ans = dp[i][m];
            id = i;
        }
    }
    cout << ans << '\n';
    while(m > 0) {
        cout << id << " ";
        id = trace[id][m];
        m--;
    }
    return 0;
}

Compilation message (stderr)

sequence.cpp: In function 'std::pair<long long int, long long int> query(long long int)':
sequence.cpp:37:17: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   37 |     if (pointer >= M.size()) {
      |         ~~~~~~~~^~~~~~~~~~~
sequence.cpp:40:19: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |     while(pointer < M.size()-1 and 1LL*M[pointer+1]*x+B[pointer+1] > 1LL*M[pointer]*x+B[pointer]) {
      |           ~~~~~~~~^~~~~~~~~~~~
sequence.cpp: In function 'int main()':
sequence.cpp:49:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   49 |         freopen("task.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
sequence.cpp:50:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |         freopen("task.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
sequence.cpp:89:12: warning: 'id' may be used uninitialized in this function [-Wmaybe-uninitialized]
   89 |         id = trace[id][m];
      |         ~~~^~~~~~~~~~~~~~

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