Submission #802439

#	Time	Username	Problem	Language	Result	Execution time	Memory
802439		borisAngelov	Election (BOI18_election)	C++17	100 / 100	439 ms	42816 KiB

election

#include <bits/stdc++.h>

using namespace std;

const int maxn = 500005;

int n;
string s;

struct segment_tree
{
    struct state
    {
        int sum;
        int max_pref;
        int max_suff;
        int ans;

        state()
        {
            sum = 0;
            max_pref = 0;
            max_suff = 0;
            ans = 0;
        }

        state(int _sum, int _max_pref, int _max_suff, int _ans)
        {
            sum = _sum;
            max_pref = _max_pref;
            max_suff = _max_suff;
            ans = _ans;
        }
    };

    state tree[4 * maxn];

    state combine(state left_child, state right_child)
    {
        state result;

        result.sum = left_child.sum + right_child.sum;
        result.max_pref = max(left_child.max_pref, left_child.sum + right_child.max_pref);
        result.max_suff = max(right_child.max_suff, right_child.sum + left_child.max_suff);
        result.ans = max(max(left_child.ans + right_child.sum, left_child.sum + right_child.ans), left_child.max_pref + right_child.max_suff);

        return result;
    }

    void build(int node, int l, int r)
    {
        if (l == r)
        {
            if (s[l] == 'T')
            {
                tree[node] = state(1, 1, 1, 1);
            }
            else
            {
                tree[node] = state(-1, 0, 0, 0);
            }

            return;
        }

        int mid = (l + r) / 2;

        build(2 * node, l, mid);
        build(2 * node + 1, mid + 1, r);

        tree[node] = combine(tree[2 * node], tree[2 * node + 1]);
    }

    state query(int node, int l, int r, int ql, int qr)
    {
        if (l > qr || r < ql)
        {
            return state(0, 0, 0, 0);
        }

        if (ql <= l && r <= qr)
        {
            return tree[node];
        }

        int mid = (l + r) / 2;

        return combine(query(2 * node, l, mid, ql, qr), query(2 * node + 1, mid + 1, r, ql, qr));
    }

    int query(int l, int r)
    {
        return query(1, 1, n, l, r).ans;
    }
};

segment_tree tree;

void fastIO()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
}

int main()
{
    fastIO();

    cin >> n >> s;
    s = '#' + s;

    tree.build(1, 1, n);

    int q;
    cin >> q;

    while (q--)
    {
        int l, r;
        cin >> l >> r;
        cout << tree.query(l, r) << "\n";
    }

    return 0;
}

• Subtask 1: 28 / 28
• Subtask 2: 54 / 54
• Subtask 3: 18 / 18