Submission #1307287

#	Time	Username	Problem	Language	Result	Execution time	Memory
1307287		pvpro	A Difficult(y) Choice (BOI21_books)	C++20	100 / 100	1 ms	404 KiB

books

#ifndef LOCAL
#pragma GCC Optimize("O3,Ofast,unroll-loops")
#pragma GCC Target("bmi,bmi2,avx,avx2")
#endif
#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;

#define f first 
#define s second 
#define mp make_pair 
#define pb push_back
#define pii pair<int, int>
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin() (x).rend()
#ifndef LOCAL
#define endl "\n"
#endif

mt19937 rnd(11);

ll skim(int i);
void answer(vector<int> v);
void impossible();

void solve(int n, int k, ll A, int s) {
    int l = 0, r = n;
    while (r - l > 1) {
        int m = (l + r) / 2;
        if (skim(m + 1) > A) {
            r = m;
        } else {
            l = m;
        }
    }
    vector<ll> pref, suff;
    for (int i = 0; i < k; ++i) {
        pref.pb(skim(i + 1));
        if (r >= k) {
            suff.pb(skim(r - k + i + 1));
        }
    }
    {
        ll s = 0;
        for (auto &x : pref) {
            s += x;
        }
        s -= pref.back();
        if (r < n && r >= k - 1 && skim(r + 1) + s <= A * 2) {
            vector<int> v;
            for (int i = 1; i < k; ++i) {
                v.pb(i);
            }
            v.pb(r + 1);
            answer(v);
            return;
        }
    }
    if (r < k) {
        impossible();
        return;
    }
    for (int i = 0; i <= k; ++i) {
        ll s = 0;
        vector<int> v;
        for (int j = 0; j < i; ++j) {
            s += pref[j];
            v.pb(j + 1);
        }
        for (int j = i; j < k; ++j) {
            s += suff[j];
            v.pb(r - k + j + 1);
        }
        if (s >= A && s <= A * 2) {
            answer(v);
            return;
        }
    }
    impossible();
}

#ifdef LOCAL
typedef long long ll;

void __attribute__((noreturn)) __attribute__((format(printf, 1, 2))) result(const char *msg, ...)
{
    va_list args;
    va_start(args, msg);
    vfprintf(stderr, msg, args);
    fprintf(stderr, "\n");
    va_end(args);
    exit(0);
}

namespace
{
    int N, K, S, sUsed;
    long long A;
    vector<long long> seq;
}

void impossible()
{
    result("Impossible (not checked): %d book(s) skimmed", sUsed);
    exit(0);
}

long long skim(int pos)
{
    printf("skim(%d): ", pos);
	if (pos<1 || pos>N) result("Invalid skim");
    printf("%lld\n", seq[pos]);
	sUsed++;
	if (sUsed>S) result("Out of books to skim");
    return seq[pos];
}

void answer(vector<int> v)
{
    printf("answer({");
    for(int i = 0; i < (int) v.size(); ++i)
    {
        printf("%d", v[i]);
        if(i + 1 != (int) v.size()) printf(", ");
    }
    printf("})\n");

	if ((int) v.size() != K) result("Invalid answer");
   	ll sum = 0;
	for(auto x: v) {
		if (x<1 || x>N) result("Invalid answer");
		sum += seq[x];
	}	
	if (sum < A || 2*A<sum) result("Wrong answer");

	result("Correct: %d book(s) skimmed", sUsed);
    exit(0);
}

int main()
{
    freopen("in.txt", "r", stdin);
    if(scanf("%d %d %lld %d", &N, &K, &A, &S) != 4)
        result("Invalid input");

    seq.resize(N + 1);
    for(int i = 1; i <= N; ++i) {
    	if(scanf("%lld", &(seq[i])) != 1) result("Invalid input");
		if(i>1 && seq[i]<=seq[i-1]) result("Invalid input");
   	}

    solve(N, K, A, S);

    result("No answer");
}
#endif

• 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