Submission #954513

#	Time	Username	Problem	Language	Result	Execution time	Memory
954513		Trisanu_Das	Sequence (APIO23_sequence)	C++17	82 / 100	2027 ms	71816 KiB

sequence

#include "sequence.h"
#include <bits/stdc++.h>
using namespace std;
 
const int N = 500050;
 
int ans = 1;
// if in range >= 0: segtree 1s = find min.
 
struct MaxSegTree {
    int size = 1;
    vector<int> seg, lazy;
    void init(int n) {
        while (size < n) size *= 2;
        seg.assign(2 * size + 5, -1e9);
        lazy.assign(2 * size + 5, 0);
    }
    void push(int id) {
        seg[id] += lazy[id];
        if (id < size) {
            for (int i = 0; i < 2; i++) {
                lazy[id * 2 + i] += lazy[id];
                continue;
            }
        }
        lazy[id] = 0;
    }
    void pull(int id) {
        seg[id] = max(seg[id * 2], seg[id * 2 + 1]);
    }
    void build(int l, int r, int id, vector<int>& v) {
        if (l == r) {
            seg[id] = v[l];
            return; 
        }
        int mid = (l + r) / 2;
        build(l, mid, id * 2, v);
        build(mid + 1, r, id * 2 + 1, v);
        pull(id);
    }
    void upd(int ql, int qr, int val, int l, int r, int id) {
        push(id);
        if (qr < l || r < ql) return;
        if (ql <= l && r <= qr) {
            lazy[id] = val;
            push(id);
            return;
        }
        int mid = (l + r) / 2;
        upd(ql, qr, val, l, mid, id * 2);
        upd(ql, qr, val, mid + 1, r, id * 2 + 1);
        pull(id);
    }
    int qry(int ql, int qr, int l, int r, int id) {
        push(id);
        if (qr < l || r < ql) return -1e9;
        if (ql <= l && r <= qr) return seg[id];
        int mid = (l + r) / 2;
        return max(qry(ql, qr, l, mid, id * 2), qry(ql, qr, mid + 1, r, id * 2 + 1));
    }
} pref0, suff0;
 
struct MinSegTree {
    int size = 1;
    vector<int> seg, lazy;
    void init(int n) {
        while (size < n) size *= 2;
        seg.assign(2 * size + 5, 1e9);
        lazy.assign(2 * size + 5, 0);
    }
    void push(int id) {
        seg[id] += lazy[id];
        if (id < size) {
            for (int i = 0; i < 2; i++) {
                lazy[id * 2 + i] += lazy[id];
                continue;
            }
        }
        lazy[id] = 0;
    }
    void pull(int id) {
        seg[id] = min(seg[id * 2], seg[id * 2 + 1]);
    }
    void build(int l, int r, int id, vector<int>& v) {
        if (l == r) {
            seg[id] = v[l];
            return; 
        }
        int mid = (l + r) / 2;
        build(l, mid, id * 2, v);
        build(mid + 1, r, id * 2 + 1, v);
        pull(id);
    }
    void upd(int ql, int qr, int val, int l, int r, int id) {
        push(id);
        if (qr < l || r < ql) return;
        if (ql <= l && r <= qr) {
            lazy[id] = val;
            push(id);
            return;
        }
        int mid = (l + r) / 2;
        upd(ql, qr, val, l, mid, id * 2);
        upd(ql, qr, val, mid + 1, r, id * 2 + 1);
        pull(id);
    }
    int qry(int ql, int qr, int l, int r, int id) {
        push(id);
        if (qr < l || r < ql) return 1e9;
        if (ql <= l && r <= qr) return seg[id];
        int mid = (l + r) / 2;
        return min(qry(ql, qr, l, mid, id * 2), qry(ql, qr, mid + 1, r, id * 2 + 1));
    }
} pref1, suff1;
 
int n;
 
bool check(int l, int r, int c) {
    int d = pref0.qry(r, r, 1, n, 1);
    if (l > 1) d -= pref0.qry(l - 1, l - 1, 1, n, 1);
    // cout << pref0.qry(r, r, 1, n, 1) << '\n';
    // cout << d << '\n';
    int w = d - c;
    int x = 0, y = 0;
    if (w <= 0) {
        if (l > 1) {
            int m = suff0.qry(l, l, 1, n, 1);
            x = max(0, suff0.qry(1, l - 1, 1, n, 1) - m);
        }
        if (r < n) {
            int m = pref0.qry(r, r, 1, n, 1);
            y = max(0, pref0.qry(r + 1, n, 1, n, 1) - m);
        }
    }
    else if (w >= 0) {
        if (l > 1) {
            int m = suff1.qry(l, l, 1, n, 1);
            x = min(0, suff1.qry(1, l - 1, 1, n, 1) - m);
        }
        if (r < n) {
            int m = pref1.qry(r, r, 1, n, 1);
            y = min(0, pref1.qry(r + 1, n, 1, n, 1) - m);
        }
    }
    // cout << w << ' ' << l << ' ' << r << ' ' << c << ' ' << x << ' ' << y << ' ';
    if (w <= 0 && x + y + w + c >= 0) {
        // cout << "true\n";
        return true;
    }
    if (w >= 0 && x + y + w - c <= 0) {
        // cout << "true\n";
        return true;
    }
    // cout << "false\n";
    return false;
}
 
int sequence(int _n, vector<int> tmp) {
    n = _n;
    vector<int> a(n+1), ps(n+1, 0);
    vector<vector<int>> pos(n+1);
    for (int i = 1; i <= n; i++) {
        a[i] = tmp[i - 1];
        pos[a[i]].push_back(i);
    }
    pref0.init(n + 1); suff0.init(n + 1);
    pref1.init(n + 1); suff1.init(n + 1);
    for (int i = 1; i <= n; i++) ps[i] = i;
    pref0.build(1, n, 1, ps); pref1.build(1, n, 1, ps);
    for (int i = 1; i <= n; i++) ps[i] = n - i + 1;
    suff0.build(1, n, 1, ps); suff1.build(1, n, 1, ps);
    for (int i = 1; i <= n; i++) {
        int l = 0, r = 0;
        for (int j = 0; j < pos[i].size(); j++) {
            pref1.upd(pos[i][j], n, -2, 1, n, 1);
            suff1.upd(1, pos[i][j], -2, 1, n, 1);
        }
        while (r < pos[i].size()) {
            if (r < l || check(pos[i][l], pos[i][r], r - l + 1)) r++;
            else l++;
            ans = max(ans, r - l);
        }
        for (int j = 0; j < pos[i].size(); j++) {
            pref0.upd(pos[i][j], n, -2, 1, n, 1);
            suff0.upd(1, pos[i][j], -2, 1, n, 1);
        }
        // for (int j = 1; j <= n; j++) cout << pref0.qry(j, j, 1, n, 1) << ' ';
        // cout << '\n';
    }
    return ans;
}

Compilation message (stderr)

sequence.cpp: In function 'int sequence(int, std::vector<int>)':
sequence.cpp:174:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  174 |         for (int j = 0; j < pos[i].size(); j++) {
      |                         ~~^~~~~~~~~~~~~~~
sequence.cpp:178:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  178 |         while (r < pos[i].size()) {
      |                ~~^~~~~~~~~~~~~~~
sequence.cpp:183:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  183 |         for (int j = 0; j < pos[i].size(); j++) {
      |                         ~~^~~~~~~~~~~~~~~

• 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: 0 / 18