Submission #974294

#	Time	Username	Problem	Language	Result	Execution time	Memory
974294		Pannda	Sequence (APIO23_sequence)	C++17	11 / 100	2067 ms	74232 KiB

sequence

#include "sequence.h"

#include <bits/stdc++.h>
using namespace std;

template<class Info, class Tag>
struct LazySegmentTree {
    int n;
    vector<Info> info;
    vector<Tag> tag;
    LazySegmentTree() : n(0) {}
    LazySegmentTree(int n_, Info v_ = Info()) {
        init(n_, v_);
    }
    template<class T>
    LazySegmentTree(vector<T> init_) {
        init(init_);
    }
    void init(int n_, Info v_ = Info()) {
        init(vector<Info>(n_, v_));
    }
    template<class T>
    void init(vector<T> init_) {
        n = init_.size();
        info.assign(4 << __lg(n), Info());
        tag.assign(4 << __lg(n), Tag());
        function<void(int, int, int)> build = [&](int p, int l, int r) {
            if (r - l == 1) {
                info[p] = init_[l];
                return;
            }
            int m = (l + r) / 2;
            build(2 * p, l, m);
            build(2 * p + 1, m, r);
            pull(p);
        };
        build(1, 0, n);
    }
    void pull(int p) {
        info[p] = info[2 * p] + info[2 * p + 1];
    }
    void apply(int p, const Tag &v) {
        info[p].apply(v);
        tag[p].apply(v);
    }
    void push(int p) {
        apply(2 * p, tag[p]);
        apply(2 * p + 1, tag[p]);
        tag[p] = Tag();
    }
    void modify(int p, int l, int r, int x, const Info &v) {
        if (r - l == 1) {
            info[p] = v;
            return;
        }
        int m = (l + r) / 2;
        push(p);
        if (x < m) {
            modify(2 * p, l, m, x, v);
        } else {
            modify(2 * p + 1, m, r, x, v);
        }
        pull(p);
    }
    void modify(int p, const Info &v) {
        modify(1, 0, n, p, v);
    }
    Info rangeQuery(int p, int l, int r, int x, int y) {
        if (l >= y || r <= x) {
            return Info();
        }
        if (l >= x && r <= y) {
            return info[p];
        }
        int m = (l + r) / 2;
        push(p);
        return rangeQuery(2 * p, l, m, x, y) + rangeQuery(2 * p + 1, m, r, x, y);
    }
    Info rangeQuery(int l, int r) {
        return rangeQuery(1, 0, n, l, r);
    }
    void rangeApply(int p, int l, int r, int x, int y, const Tag &v) {
        if (l >= y || r <= x) {
            return;
        }
        if (l >= x && r <= y) {
            apply(p, v);
            return;
        }
        int m = (l + r) / 2;
        push(p);
        rangeApply(2 * p, l, m, x, y, v);
        rangeApply(2 * p + 1, m, r, x, y, v);
        pull(p);
    }
    void rangeApply(int l, int r, const Tag &v) {
        return rangeApply(1, 0, n, l, r, v);
    }
    template<class F>
    int findFirst(int p, int l, int r, int x, int y, F &&pred) {
        if (l >= y || r <= x) {
            return -1;
        }
        if (l >= x && r <= y && !pred(info[p])) {
            return -1;
        }
        if (r - l == 1) {
            return l;
        }
        int m = (l + r) / 2;
        push(p);
        int res = findFirst(2 * p, l, m, x, y, pred);
        if (res == -1) {
            res = findFirst(2 * p + 1, m, r, x, y, pred);
        }
        return res;
    }
    template<class F>
    int findFirst(int l, int r, F &&pred) {
        return findFirst(1, 0, n, l, r, pred);
    }
    template<class F>
    int findLast(int p, int l, int r, int x, int y, F &&pred) {
        if (l >= y || r <= x) {
            return -1;
        }
        if (l >= x && r <= y && !pred(info[p])) {
            return -1;
        }
        if (r - l == 1) {
            return l;
        }
        int m = (l + r) / 2;
        push(p);
        int res = findLast(2 * p + 1, m, r, x, y, pred);
        if (res == -1) {
            res = findLast(2 * p, l, m, x, y, pred);
        }
        return res;
    }
    template<class F>
    int findLast(int l, int r, F &&pred) {
        return findLast(1, 0, n, l, r, pred);
    }
};

struct Tag {
    int add = 0;
    void apply(const Tag &t) & {
        add += t.add;
    }
};

constexpr int INF = 1e9;
struct Info {
    int mn = INF;
    int mx = -INF;
    void apply(const Tag &t) & {
        mn += t.add;
        mx += t.add;
    }
    Info operator+(const Info &b) {
        return {min(mn, b.mn), max(mx, b.mx)};
    }
};

struct Fenwick {
    int n;
    vector<int> bit;

    Fenwick(int n) : n(n), bit(n + 1, 0) {}

    void add(int i, int delta) {
        for (i++; i <= n; i += i & -i) {
            bit[i] += delta;
        }
    }

    int sum(int i) {
        int res = 0;
        for (; i > 0; i -= i & -i) {
            res += bit[i];
        }
        return res;
    }

    int sum(int ql, int qr) {
        return sum(qr) - sum(ql);
    }
};

int sequence(int n, vector<int> a) {
    vector<vector<int>> mp(n);
    for (int i = 0; i < n; i++) {
        a[i]--;
        mp[a[i]].push_back(i);
    }

    auto ok = [&](int x) -> bool {
        Fenwick fen(n);
        vector<Info> lr(n + 1), rl(n + 1);
        for (int i = 0; i <= n; i++) {
            lr[i] = {-i, -i};
            rl[i] = {i - n, i - n};
        }
        LazySegmentTree<Info, Tag> seg_le_lr(lr);
        LazySegmentTree<Info, Tag> seg_le_rl(rl);

        for (int med = 0; med < n; med++) {
            for (int i : mp[med]) {
                fen.add(i, +1);
                seg_le_lr.rangeApply(i + 1, n + 1, {+2});
                seg_le_rl.rangeApply(0, i + 1, {+2});
            }
            for (int ii = 0; ii + x <= mp[med].size(); ii++) {
                int l = mp[med][ii];
                int r = mp[med][ii + x - 1] + 1;
                int lem = fen.sum(l, r);
                int gem = (r - l) - lem + x;
                if (2 * lem >= r - l && 2 * gem >= r - l) return true;
                if (2 * lem < r - l) {
                    int val = 2 * lem - r + l; // < 0
                    int up = seg_le_lr.rangeQuery(r, n + 1).mx - seg_le_lr.rangeQuery(r, r + 1).mx + seg_le_rl.rangeQuery(0, l + 1).mx - seg_le_rl.rangeQuery(l, l + 1).mx;
                    if (val + up >= 0) return true;
                } else {
                    int val = 2 * gem - r + l; // < 0
                    int up = seg_le_lr.rangeQuery(r, n + 1).mn - seg_le_lr.rangeQuery(r, r + 1).mn + seg_le_rl.rangeQuery(0, l + 1).mn - seg_le_rl.rangeQuery(l, l + 1).mn;
                    up = -up;
                    if (val + up >= 0) return true;
                }
            }
        }
        return false;
    };

    int ans = [&]() -> int {
        int l = 1, r = n;
        while (l < r) {
            int m = (l + r + 1) >> 1;
            if (ok(m)) {
                l = m;
            } else {
                r = m - 1;
            }
        }
        return l;
    }();

    return ans;
}

Compilation message (stderr)

sequence.cpp: In lambda function:
sequence.cpp:215:37: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  215 |             for (int ii = 0; ii + x <= mp[med].size(); ii++) {
      |                              ~~~~~~~^~~~~~~~~~~~~~~~~

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