Submission #854460

#	Time	Username	Problem	Language	Result	Execution time	Memory
854460		dxz05	Sequence (APIO23_sequence)	C++17	20 / 100	1832 ms	76064 KiB

sequence

#include "sequence.h"
#include <bits/stdc++.h>

using namespace std;

template <typename T>
struct SegmentTree{
    struct node{
        T sum;
        T Min;
        T Max;
        T lazy;
        bool isUpdated;
        node(){
            sum = Min = Max = 0;
            lazy = 0;
            isUpdated = false;
        };
        node(T x){
            sum = Min = Max = x;
            lazy = 0;
            isUpdated = false;
        }
    };

    vector<node> tree;

    node neutral_element;

    inline void combine(node &par, node lf, node rg){
        par.sum = lf.sum + rg.sum;
        par.Min = min(lf.Min, rg.Min);
        par.Max = max(lf.Max, rg.Max);
    }

    int _begin, _end;

    inline void init(int n){
        _begin = 0;
        _end = n - 1;
        neutral_element.Min = 2 * n;
        neutral_element.Max = -2 * n;
        tree.resize(n * 4 + 5);
    }

    inline void upd(int v, int tl, int tr, T lazy){
        tree[v].sum += lazy * (tr - tl + 1);
        tree[v].Min += lazy;
        tree[v].Max += lazy;
        tree[v].isUpdated = true;
        tree[v].lazy += lazy;
    }

    inline void push(int v, int tl, int tr){
        if (tl == tr || !tree[v].isUpdated) return;

        int tm = (tl + tr) >> 1;
        upd(v << 1, tl, tm, tree[v].lazy);
        upd(v << 1 | 1, tm + 1, tr, tree[v].lazy);

        tree[v].lazy = 0;
        tree[v].isUpdated = false;
    }

    inline void update(int v, int tl, int tr, int l, int r, T val){
        push(v, tl, tr);
        if (l <= tl && tr <= r){
            upd(v, tl, tr, val);
            return;
        }
        if (tl > r || tr < l) return;

        int tm = (tl + tr) >> 1;
        update(v << 1, tl, tm, l, r, val);
        update(v << 1 | 1, tm + 1, tr, l, r, val);

        combine(tree[v], tree[v << 1], tree[v << 1 | 1]);
    }

    inline void update(int l, int r, T val){
        update(1, _begin, _end, l, r, val);
    }

    inline node get(int v, int tl, int tr, int l, int r){
        push(v, tl, tr);
        if (l <= tl && tr <= r) return tree[v];
        if (tl > r || tr < l) return neutral_element;
        int tm = (tl + tr) >> 1;
        node res;
        combine(res, get(v << 1, tl, tm, l, r), get(v << 1 | 1, tm + 1, tr, l, r));
        return res;
    }

    inline node get(int l, int r){
        return get(1, _begin, _end, l, r);
    }

    inline int get(int i){
        return get(i, i).sum;
    }

};

int sequence(int N, std::vector<int> A) {
    A.insert(A.begin(), 0);

    vector<vector<int>> pos(N + 1);
    for (int i = 1; i <= N; i++){
        pos[A[i]].push_back(i);
    }

    int ans = 1;
    int t = 0;
    for (int i = 1; i <= N; i++){
        if (i == 1 || A[i] == A[i - 1]){
            t++;
        } else {
            t = 1;
        }
        ans = max(ans, t);
    }

    SegmentTree<int> st;
    st.init(N + 1);
    for (int i = 1; i <= N; i++){
        st.update(i, N, 1);
    }

    for (int x = 1; x <= N; x++){
        if (pos[x].empty()) continue;

        for (int i : pos[x]){ // making 0
            st.update(i, N, -1);
        }

        {
            int i = pos[x].front(), j = pos[x].back();
            int f = pos[x].size();

            int sum = st.get(j) - st.get(i - 1);

            if (abs(sum) <= f) ans = max(ans, f);

            int l1 = st.get(i) - st.get(0, i).Max;
            int r1 = st.get(i) - st.get(0, i).Min;

            int l2 = st.get(j, N).Min - st.get(j);
            int r2 = st.get(j, N).Max - st.get(j);

            l1 = min(l1, 0), l2 = min(l2, 0);
            r1 = max(r1, 0), r2 = max(r2, 0);

            int need;
            if (sum < -f) {
                need = -f - sum;
            } else {
                need = f - sum;
            }

            if (l1 + l2 <= need && need <= r1 + r2) ans = max(ans, f);
        }

        for (int i : pos[x]){ // making -1
            st.update(i, N, -1);
        }
    }

    return ans;
}

• Subtask 1: 0 / 11
• Subtask 2: 0 / 17
• Subtask 3: 7 / 7
• Subtask 4: 0 / 12
• Subtask 5: 13 / 13
• Subtask 6: 0 / 22
• Subtask 7: 0 / 18