Submission #837707

#	Time	Username	Problem	Language	Result	Execution time	Memory
837707		GrindMachine	Sequence (APIO23_sequence)	C++17	100 / 100	927 ms	74076 KiB

sequence

// Om Namah Shivaya

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl

#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a, b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a, b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif

/*

refs:
https://codeforces.com/blog/entry/116491?#comment-1031309
edi

*/

const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

#include "sequence.h"

template<typename T>
struct segtree {
    // https://codeforces.com/blog/entry/18051

    /*=======================================================*/

    struct data {
        int mnpref,mxpref,mnsuff,mxsuff,sum;
        data(){
            mnpref = mxpref = mnsuff = mxsuff = sum = 0;
        }
    };

    data neutral = data();

    data merge(data &left, data &right) {
        data curr;

        curr.mnpref = min(left.mnpref,left.sum+right.mnpref);
        curr.mxpref = max(left.mxpref,left.sum+right.mxpref);
        curr.mnsuff = min(right.mnsuff,right.sum+left.mnsuff);
        curr.mxsuff = max(right.mxsuff,right.sum+left.mxsuff);
        curr.sum = left.sum+right.sum;

        return curr;
    }

    void create(int i, T v) {
        tr[i].mnpref = tr[i].mnsuff = min(v,0);
        tr[i].mxpref = tr[i].mxsuff = max(v,0);
        tr[i].sum = v;
    }

    void modify(int i, T v) {
        tr[i].mnpref = tr[i].mnsuff = min(v,0);
        tr[i].mxpref = tr[i].mxsuff = max(v,0);
        tr[i].sum = v;
    }

    /*=======================================================*/

    int n;
    vector<data> tr;

    segtree() {

    }

    segtree(int siz) {
        init(siz);
    }

    void init(int siz) {
        n = siz;
        tr.assign(2 * n, neutral);
    }

    void build(vector<T> &a, int siz) {
        rep(i, siz) create(i + n, a[i]);
        rev(i, n - 1, 1) tr[i] = merge(tr[i << 1], tr[i << 1 | 1]);
    }

    void pupd(int i, T v) {
        modify(i + n, v);
        for (i = (i + n) >> 1; i; i >>= 1) tr[i] = merge(tr[i << 1], tr[i << 1 | 1]);
    }

    data query(int l, int r) {
        data resl = neutral, resr = neutral;

        for (l += n, r += n; l <= r; l >>= 1, r >>= 1) {
            if (l & 1) resl = merge(resl, tr[l++]);
            if (!(r & 1)) resr = merge(tr[r--], resr);
        }

        return merge(resl, resr);
    }
};

int sequence(int n, std::vector<int> a) {
    a.insert(a.begin(),0);
    vector<int> pos[n+5];
    rep1(i,n) pos[a[i]].pb(i);

    // val >= x: st1[i] = 1, else -1
    // val > x: st2[i] = 1, else -1

    segtree<int> st1(n+5);
    rep1(i,n) st1.pupd(i,1);

    auto st2 = st1;

    int ans = 0;

    rep1(x,n){
        auto &p = pos[x];
        int siz = sz(p);

        trav(i,p){
            st2.pupd(i,-1);
        }

        int ptr = 0;

        rep(i,siz){
            while(ptr < siz){
                int l = p[i], r = p[ptr];

                int mx_sum = st1.query(1,l-1).mxsuff + st1.query(l,r).sum + st1.query(r+1,n).mxpref;
                int mn_sum = st2.query(1,l-1).mnsuff + st2.query(l,r).sum + st2.query(r+1,n).mnpref;

                if((ll)mx_sum*mn_sum <= 0){
                    ptr++;
                }
                else{
                    break;
                }
            }

            int cnt = ptr-i;
            amax(ans,cnt);
        }
    
        trav(i,p){
            st1.pupd(i,-1);
        }
    }

    return ans;
}

• Subtask 1: 11 / 11
• Subtask 2: 17 / 17
• Subtask 3: 7 / 7
• Subtask 4: 12 / 12
• Subtask 5: 13 / 13
• Subtask 6: 22 / 22
• Subtask 7: 18 / 18