Submission #1308011

#	Time	Username	Problem	Language	Result	Execution time	Memory
1308011		damager	Election (BOI18_election)	C++20	0 / 100	1 ms	332 KiB

election

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

struct Node {
    int sum;
    int minPref;
    int minSuff;
};

Node mergeNode(const Node &A, const Node &B) {
    Node res;
    res.sum = A.sum + B.sum;
    res.minPref = min(A.minPref, A.sum + B.minPref);
    res.minSuff = min(B.minSuff, B.sum + A.minSuff);
    return res;
}

class SegmentTree {
private:
    int n;
    vector<Node> tree;

    void build(int idx, int l, int r, const vector<int> &arr) {
        if (l == r) {
            tree[idx].sum = arr[l];
            tree[idx].minPref = min(0, arr[l]);
            tree[idx].minSuff = min(0, arr[l]);
            return;
        }
        int mid = (l + r) / 2;
        build(2 * idx, l, mid, arr);
        build(2 * idx + 1, mid + 1, r, arr);
        tree[idx] = mergeNode(tree[2 * idx], tree[2 * idx + 1]);
    }

    Node query(int idx, int l, int r, int ql, int qr) {
        if (ql > r || qr < l) {
            return {0, 0, 0};  
        }
        if (ql <= l && r <= qr) {
            return tree[idx];
        }
        int mid = (l + r) / 2;
        Node left = query(2 * idx, l, mid, ql, qr);
        Node right = query(2 * idx + 1, mid + 1, r, ql, qr);
        return mergeNode(left, right);
    }

public:
    SegmentTree(const vector<int> &arr) {
        n = arr.size();
        tree.resize(4 * n);
        build(1, 0, n - 1, arr);
    }

    int getAnswer(int l, int r) {
        Node res = query(1, 0, n - 1, l, r);
        return max(-res.minPref, -res.minSuff);
    }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
    cin >> N;

    string s;
    cin >> s;

    vector<int> arr(N);
    for (int i = 0; i < N; i++) {
        arr[i] = (s[i] == 'C' ? 1 : -1);
    }

    SegmentTree st(arr);

    int Q;
    cin >> Q;
    while (Q--) {
        int L, R;
        cin >> L >> R;
        cout << st.getAnswer(L - 1, R - 1) << "\n";
    }

    return 0;
}

• Subtask 1: 0 / 28
• Subtask 2: 0 / 54
• Subtask 3: 0 / 18