oj.uz

Submission #735780

# Submission time Handle Problem Language Result Execution time Memory
735780 2023-05-04T16:15:12 Z GrindMachine Election (BOI18_election) C++17
100 / 100
 517 ms 60764 KB 
// Om Namah Shivaya

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl

#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a, b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a, b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif

/*

refs:
edi


let a[i] = 1 for 'C' and a[i] = -1 for 'T'

if only pref condition is there, then following greedy works:
iterate from l to r, add a[i] to sum
if sum < 0, then ignore curr guy and make sum = 0
add 1 to ans every time this op is done

how to handle suff cond?
first run pref, and find out the guys to ignore
when doing for pref, we make ignore ops as much to the right as possible
so when doing suff ops, this means ignore ops will come earlier
which will benefit the suff

so in short:
run pref, mark guys to ignore
run suff, ignore marked guys and ignore any addl guys if required

*/

const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

template<typename T>
struct segtree {
    // https://codeforces.com/blog/entry/18051

    /*=======================================================*/

    struct data {
        ll mnsuff, sum;
    };

    data neutral = {0, 0};

    data merge(data &left, data &right) {
        data curr;

        curr.mnsuff = min(right.mnsuff, right.sum + left.mnsuff);
        curr.sum = left.sum + right.sum;

        return curr;
    }

    void create(int i, T v) {
        tr[i] = {min(v, 0ll), v};
    }

    void modify(int i, T v) {
        tr[i] = {min(v, 0ll), v};
    }

    /*=======================================================*/

    int n;
    vector<data> tr;

    segtree() {

    }

    segtree(int siz) {
        init(siz);
    }

    void init(int siz) {
        n = siz;
        tr.assign(2 * n, neutral);
    }

    void build(vector<T> &a, int siz) {
        rep(i, siz) create(i + n, a[i]);
        rev(i, n - 1, 1) tr[i] = merge(tr[i << 1], tr[i << 1 | 1]);
    }

    void pupd(int i, T v) {
        modify(i + n, v);
        for (i = (i + n) >> 1; i; i >>= 1) tr[i] = merge(tr[i << 1], tr[i << 1 | 1]);
    }

    data query(int l, int r) {
        data resl = neutral, resr = neutral;

        for (l += n, r += n; l <= r; l >>= 1, r >>= 1) {
            if (l & 1) resl = merge(resl, tr[l++]);
            if (!(r & 1)) resr = merge(tr[r--], resr);
        }

        return merge(resl, resr);
    }
};

void solve(int test_case)
{
    ll n; cin >> n;
    vector<ll> a(n + 5);
    rep1(i, n) {
        char ch; cin >> ch;
        if (ch == 'C') a[i] = 1;
        else a[i] = -1;
    }

    ll q; cin >> q;
    vector<pll> here[n + 5];

    rep1(i, q) {
        ll l, r; cin >> l >> r;
        here[l].pb({r, i});
    }

    segtree<ll> st(n + 5);
    st.build(a, n + 1);

    deque<ll> dq;
    vector<ll> ans(q + 5);

    rev(l, n, 1) {
        if (a[l] == -1) {
            dq.push_front(l);
            st.pupd(l, 0);
        }
        else {
            if (!dq.empty()) {
                ll i = dq.front();
                st.pupd(i, -1);
                dq.pop_front();
            }
        }

        for (auto [r, id] : here[l]) {
            ll pref_ignored = upper_bound(all(dq), r) - dq.begin();
            ll suff_ignored = -st.query(l, r).mnsuff;
            ans[id] = pref_ignored + suff_ignored;
        }
    }

    rep1(i, q) cout << ans[i] << endl;
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;

    rep1(i, t) {
        solve(i);
    }

    return 0;
}

Subtask #1
28.0 / 28.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 468 KB Output is correct
2 Correct 1 ms 468 KB Output is correct
3 Correct 1 ms 468 KB Output is correct
4 Correct 2 ms 468 KB Output is correct
5 Correct 1 ms 468 KB Output is correct

Subtask #2
54.0 / 54.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 468 KB Output is correct
2 Correct 1 ms 468 KB Output is correct
3 Correct 1 ms 468 KB Output is correct
4 Correct 2 ms 468 KB Output is correct
5 Correct 1 ms 468 KB Output is correct
6 Correct 43 ms 7368 KB Output is correct
7 Correct 41 ms 8212 KB Output is correct
8 Correct 36 ms 8008 KB Output is correct
9 Correct 39 ms 8136 KB Output is correct
10 Correct 39 ms 8184 KB Output is correct
11 Correct 51 ms 8492 KB Output is correct
12 Correct 54 ms 8424 KB Output is correct
13 Correct 51 ms 8632 KB Output is correct
14 Correct 39 ms 8396 KB Output is correct
15 Correct 37 ms 8256 KB Output is correct

Subtask #3
18.0 / 18.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 468 KB Output is correct
2 Correct 1 ms 468 KB Output is correct
3 Correct 1 ms 468 KB Output is correct
4 Correct 2 ms 468 KB Output is correct
5 Correct 1 ms 468 KB Output is correct
6 Correct 43 ms 7368 KB Output is correct
7 Correct 41 ms 8212 KB Output is correct
8 Correct 36 ms 8008 KB Output is correct
9 Correct 39 ms 8136 KB Output is correct
10 Correct 39 ms 8184 KB Output is correct
11 Correct 51 ms 8492 KB Output is correct
12 Correct 54 ms 8424 KB Output is correct
13 Correct 51 ms 8632 KB Output is correct
14 Correct 39 ms 8396 KB Output is correct
15 Correct 37 ms 8256 KB Output is correct
16 Correct 461 ms 58620 KB Output is correct
17 Correct 311 ms 57676 KB Output is correct
18 Correct 369 ms 56592 KB Output is correct
19 Correct 375 ms 57716 KB Output is correct
20 Correct 442 ms 57548 KB Output is correct
21 Correct 517 ms 60144 KB Output is correct
22 Correct 468 ms 59512 KB Output is correct
23 Correct 495 ms 60764 KB Output is correct
24 Correct 454 ms 59736 KB Output is correct
25 Correct 429 ms 58780 KB Output is correct