Submission #671080

#	Time	Username	Problem	Language	Result	Execution time	Memory
671080		SirCovidThe19th	Index (COCI21_index)	C++17	110 / 110	1266 ms	58688 KiB

index

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

template<class T, int sz> struct persistentSegTree{
    static const int maxSz = sz * 31;

    T seg[maxSz]; int idx = 1, lc[maxSz], rc[maxSz];

    void dup(int &i){
        lc[idx] = lc[i];
        rc[idx] = rc[i];
        seg[idx] = seg[i];
        i = idx; idx++;
    }
    void upd(int p, int &i, int l = 0, int r = 2e5 + 5){
        dup(i);
        if (l == r){ seg[i] = 1; return; }

        int mid = (l + r) / 2;
        if (p <= mid) upd(p, lc[i], l, mid);
        else upd(p, rc[i], mid + 1, r);

        seg[i] = seg[lc[i]] + seg[rc[i]];
    }
    T qry(int ql, int qr, int i, int l = 0, int r = 2e5 + 5){
        if (qr < l or ql > r or !i) return 0;
        if (l >= ql and r <= qr) return seg[i];
        int mid = (l + r) / 2;
        return qry(ql, qr, lc[i], l, mid) + qry(ql, qr, rc[i], mid + 1, r);
    }
};

const int mx = 2e5 + 5;

int n, q, root[mx]; vector<int> nums[mx]; persistentSegTree<int, mx> pseg;

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); 
    cin >> n >> q;
    for (int i = 1; i <= n; i++){
        int p; cin >> p;
        nums[p].push_back(i);
    }
    for (int p = mx - 2; p; p--){ //p[i] <= 2e5
        root[p] = root[p + 1];
        for (int i : nums[p])
            pseg.upd(i, root[p]);
    }
    while (q--){
        int l, r; cin >> l >> r;

        int lo = 0, hi = mx;
        while (lo < hi){
            int mid = (lo + hi + 1) / 2;
            //How many elems >= mid in [l...r]?
            (pseg.qry(l, r, root[mid]) >= mid) ? lo = mid : hi = mid - 1;
        }
        cout<<lo<<"\n";
    }
}

• Subtask 1: 20 / 20
• Subtask 2: 40 / 40
• Subtask 3: 50 / 50