Submission #573711

#	Time	Username	Problem	Language	Result	Execution time	Memory
573711		talant117408	A Difficult(y) Choice (BOI21_books)	C++17	100 / 100	2 ms	352 KiB

books

#include "books.h"
#include <bits/stdc++.h>

#ifndef EVAL
#include "grader.cpp"
#endif
 
using namespace std;
 
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
 
#define pb                  push_back
#define mp                  make_pair
#define all(v)              (v).begin(),(v).end()
#define sz(v)               int((v).size())
#define do_not_disturb      ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl                '\n'
 
int mod = 1e9+7;
 
ll modulo(ll a) {
    return ((a % mod) + mod) % mod;
}
 
ll add(ll a, ll b) {
    return modulo(a + b);
}
 
ll mult(ll a, ll b) {
    return modulo(a * b);
}
 
ll binpow(ll a, ll b) {
    ll res = 1;
    while (b) {
        if (b&1) {
            res = mult(res, a);
        }
        a = mult(a, a);
        b >>= 1;
    }
    return res;
}

const int MX = 1e5+7;
ll val[MX];

ll ask(int i) {
    if (val[i] > 0) return val[i];
    return val[i] = skim(i);
}

void solve(int n, int k, long long a, int s) {
    vector <ll> pref, suff;
    ll sum = 0, l = 1, r = n+1;
    while (l < r) {
        int mid = (l+r) >> 1;
        if (ask(mid) > a) {
            r = mid;
        }
        else {
            l = mid+1;
        }
    }
    
    for (int i = 1; i < k; i++) {
        sum += ask(i);
    }
    int ind = l;
    if (ind < k || sum + ask(k) > 2*a) {
        impossible();
        return;
    }
    if (ind != n+1 && a <= ask(ind)+sum && ask(ind)+sum <= a*2) {
        vector <int> ans(k);
        iota(all(ans), 1);
        ans.back() = ind;
        answer(ans);
        return;
    }
    
    pref.pb(0); suff.pb(0);
    for (int i = 1; i <= k; i++) {
        pref.pb(ask(i)+pref.back());
    }
    for (int i = ind-1; i >= ind-k; i--) {
        suff.pb(ask(i)+suff.back());
    }
    
    for (int i = 0; i <= k; i++) {
        sum = pref[k-i]+suff[i];
        if (sum > 2*a) impossible();
        if (a <= sum && sum <= 2*a) {
            vector <int> ans;
            for (int j = 1; j <= k-i; j++) {
                ans.pb(j);
            }
            for (int j = 1; j <= i; j++) {
                ans.pb(ind-j);
            }
            answer(ans);
            return;
        }
    }
    
    impossible();
}
/*
15 3 42 170
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
*/

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 20 / 20
• Subtask 7: 20 / 20