Submission #1205632

#	Time	Username	Problem	Language	Result	Execution time	Memory
1205632		pigsyy	Election (BOI18_election)	C++20	100 / 100	619 ms	42020 KiB

election

#include <bits/stdc++.h>
using namespace std;
#define mat array<array<int, 3>, 3>
#define _(i, j) max({a[i][0] + b[0][j], a[i][1] + b[1][j], a[i][2] + b[2][j]})
mat operator* (mat a, mat b) {
    return {_(0, 0), _(0, 1), _(0, 2), 
            _(1, 0), _(1, 1), _(1, 2), 
            _(2, 0), _(2, 1), _(2, 2)};
}

const int maxn = 500005, inf = 1 << 30;

int n, q, m;
string s;
mat tr[maxn * 4];
int pref[maxn];

int main() {
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);

    cin >> n >> s >> q;
    s = ' ' + s, m = (1 << __lg(n) + 1) - 1;

    for (int i = 1; i <= n; i ++) {
        tr[i + m] = {s[i] == 'C' ? 1 : -1, 0, -inf, -inf, 0, -inf, 0, -inf, 0};
        pref[i] = pref[i - 1] + (s[i] == 'C');
    }
    for (int i = m; i >= 1; i -- )
        tr[i] = tr[i << 1] * tr[i << 1 | 1];

    while (q -- ) {
        int l, r;
        cin >> l >> r;

        int L = l + m, R = r + m;
        mat P = {0, 0, 0, -inf, -inf, -inf, -inf, -inf, -inf}, Q = {0, 0, 0, 0, 0, 0, 0, 0, 0};
        for (; L <= R; L >>= 1, R >>= 1) {
            if (L & 1) P = P * tr[L ++];
            if (~R & 1) Q = tr[R --] * Q;
        }
        mat ans = P * Q;
        
        int sum = ans[0][0], mx = max(ans[0][1], sum), res = 2 * (pref[r] - pref[l - 1]) - sum;
        cout << r - l + 1 - (res - mx + sum) << endl;
    }

    return 0;
}

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