Submission #1236985

#	Time	Username	Problem	Language	Result	Execution time	Memory
1236985		12baater	Horses (IOI15_horses)	C++20	54 / 100	365 ms	64036 KiB

horses

#include "horses.h"
#include <stack>
#include <iostream>
#include <vector>
#include <algorithm>
#include <set>

using namespace std;
typedef long long ll;

const ll MOD = 1E9 + 7;
const int MAXN = 500050;
int n;
vector<int> x(MAXN);
vector<int> y(MAXN);
set<int> valid_indices;

struct ST {
    int n;
    vector<ll> seg;

    ST(int N) : seg(4*N) {
        int s = 1;
        for (; s < N; s <<= 1);
        n = N;

    }

    void update(int pos, int val) {
        pos += n;
        seg[pos] = val;
        pos >>= 1;
        while (pos > 0) {
            seg[pos] = (seg[pos*2] * seg[pos*2 + 1])%MOD;
            pos >>= 1;
        }
    }

    ll query(int l, int r) {
        l += n;
        r += n;
        ll ret = 1;
        while (l < r) {
            if (l&1) { ret *= seg[l++]; ret %= MOD; }
            if (r&1) { ret *= seg[--r]; ret %= MOD; }
            l >>= 1;
            r >>= 1;
        }
        return ret%MOD;
    }
};

struct maxST {
    ll n;
    vector<ll> seg;

    maxST(ll N) : seg(4*N) {
        int s = 1;
        for (; s < N; s <<= 1);
        n = s;
    }

    void update(ll pos, ll val) {
        pos += n;
        seg[pos] = val;
        pos >>= 1;
        while (pos > 0) {
            seg[pos] = max(seg[pos*2], seg[pos*2 + 1]);
            pos >>= 1;
        }
    }

    ll query(ll l, ll r) {
        l += n;
        r += n;
        ll ret = 0;
        while (l < r) {
            if (l&1) ret = max(ret, seg[l++]);
            if (r&1) ret = max(ret, seg[--r]);
            l >>= 1;
            r >>= 1;
        }
        return ret;
    }
};

ST tree(MAXN);
maxST maxTree(MAXN);

int find_best() {
    stack<int> to_process;
    auto it = valid_indices.rbegin();
    for (int i = 0; i <= 100; i++) {
        if (it == valid_indices.rend()) {
            if (to_process.empty()) {
                to_process.push(0);
                break;
            } else if (to_process.top() != 0) {
                to_process.push(0);
                break;
            }
            break;
        }
        to_process.push(*it);
        it++;
    }

    int bestInd = 0;
    int current = 0;
    ll tot = 1;
    ll currentVal = 0;
    ll best = 0;

    current = to_process.top();
    to_process.pop();

    while (!to_process.empty()) {
        int next = to_process.top(); to_process.pop();
        tot *= x[current];
        currentVal = maxTree.query(current, next);
        if (tot * currentVal >= best) {
            best = currentVal;
            bestInd = current;
            tot = 1;
        }
        current = next;
    }

    // currentVal = maxTree.query(current, n);
    // tot *= x[current];
    // if (tot * currentVal >= best) {
    //     best = currentVal;
    //     bestInd = current;
    // }
    // for (int i = start+1; i < n; i++) {
    //     tot *= x[i];
    //     if (tot * y[i] >= y[bestInd]) {
    //         bestInd = i;
    //         tot = 1;
    //     }
    // }
    return static_cast<int>((tree.query(0, bestInd+1) * best) % MOD);
}


int solve() {
    // int num = max(0, n-1001);
    // int ind = find_best(num);
    // ll horseNum = tree.query(0, ind+1);
    // ll cashNum = y[ind];
    // cout << horseNum << " " << cashNum << endl;
    return find_best();
}


int init(int N, int X[], int Y[]) {
    valid_indices.insert(N);
    n = N;
    for (int i = 0; i < N; i++) {
        x[i] = X[i];
        y[i] = Y[i];
        tree.update(i, x[i]);
        maxTree.update(i, y[i]);
        if (x[i] != 1) {
            valid_indices.insert(i);
        }
    }
    return solve();
}

int updateX(int pos, int val) {
    x[pos] = val;
    tree.update(pos, val);
    if (val == 1) {
        valid_indices.erase(pos);
    } else {
        valid_indices.insert(pos);
    }
    return solve();
}

int updateY(int pos, int val) {
    maxTree.update(pos, val);
    y[pos] = val;
    return solve();
}

• Subtask 1: 17 / 17
• Subtask 2: 17 / 17
• Subtask 3: 20 / 20
• Subtask 4: 0 / 23
• Subtask 5: 0 / 23