Submission #419613

#	Time	Username	Problem	Language	Result	Execution time	Memory
419613		Collypso	Xylophone (JOI18_xylophone)	C++17	100 / 100	93 ms	332 KiB

xylophone

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vt vector
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int) (x).size()
#pragma GCC optimize ("O3")
#pragma GCC optimize ("O2")
#define F first
#define S second
//#define endl '\n'
//#define int long long

using namespace std;

int query(int s, int t);
void answer(int i, int a);

void solve(int N)
{
	int f, l = 1, r = N;
	while(l <= r)
    {
        int m = (l + r) / 2;
        if (query(m, N) == N - 1) f = m, l = m + 1;
        else r = m - 1;
    }
    vt<int> ans(N + 1), used(N + 1);
    used[1] = ans[f] = 1;
    for(int i = f - 1, q, a, b; i >= 1; i--)
    {
        q = query(i, i + 1), a = ans[i + 1] - q, b = ans[i + 1] + q;
        if (a < 1 || used[a]) used[b] = 1, ans[i] = b;
        else if (b > N || used[b]) used[a] = 1, ans[i] = a;
        else
        {
            int mx = max(ans[i + 2], ans[i + 1]);
            int mn = min(ans[i + 2], ans[i + 1]);
            int new_q = query(i, i + 2);
            if (b > mx && new_q == (b - mn)) used[b] = 1, ans[i] = b;
            else if (b < mx && new_q == (mx - mn)) used[b] = 1, ans[i] = b;
            else used[a] = 1, ans[i] = a;
        }
    }
    for(int i = f + 1, q, a, b; i <= N; i++)
    {
        q = query(i - 1, i), a = ans[i - 1] - q, b = ans[i - 1] + q;
        if (a < 1 || used[a]) used[b] = 1, ans[i] = b;
        else if (b > N || used[b]) used[a] = 1, ans[i] = a;
        else
        {
            int mx = max(ans[i - 2], ans[i - 1]);
            int mn = min(ans[i - 2], ans[i - 1]);
            int new_q = query(i - 2, i);
            if (b > mx && new_q == (b - mn)) used[b] = 1, ans[i] = b;
            else if (b < mx && new_q == (mx - mn)) used[b] = 1, ans[i] = b;
            else used[a] = 1, ans[i] = a;
        }
    }
    for(int i = 1; i <= N; i++) answer(i, ans[i]);
    //cout << endl;
}

Compilation message (stderr)

xylophone.cpp: In function 'void solve(int)':
xylophone.cpp:48:13: warning: 'f' may be used uninitialized in this function [-Wmaybe-uninitialized]
   48 |     for(int i = f + 1, q, a, b; i <= N; i++)
      |             ^

• Subtask 1: 11 / 11
• Subtask 2: 36 / 36
• Subtask 3: 53 / 53