Submission #797271

#	Time	Username	Problem	Language	Result	Execution time	Memory
797271		n3rm1n	JJOOII 2 (JOI20_ho_t2)	C++17	100 / 100	8 ms	3284 KiB

ho_t2

#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
const int MAXN = 2e5 + 10;
void speed()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
}
int n, k;
char s[MAXN];
void read()
{
    cin >> n >> k;
    for (int i = 1; i <= n; ++ i)
        cin >> s[i];
}
int dp0[MAXN], dp1[MAXN];
int cnt[MAXN];
void precompute()
{
    deque < int > q;
    for (int i = n; i >= 1; -- i)
    {
        if(s[i] == 'J')q.push_back(i);
        if(q.size() > k)q.pop_front();

        if(q.size() < k)dp0[i] = n+1;
        else dp0[i] = q.front();
    }
    q.clear();
    for (int i = 1; i <= n; ++ i)
    {
        if(s[i] == 'I')q.push_back(i);
        if(q.size() > k)q.pop_front();

        if(q.size() < k)dp1[i] = 0;
        else dp1[i] = q.front();
    }
    for (int i = 1; i <= n; ++ i)
    {
        cnt[i] = cnt[i-1];
        if(s[i] == 'O')cnt[i] ++;
    }
   /* for (int i = 1; i <= n; ++ i)
        cout << dp0[i] << " ";
    cout << endl;
    for (int i = 1; i <= n; ++ i)
        cout << dp1[i] << " ";
    cout << endl; */
}
bool check(int x)
{
    for (int i = 0; i <= x; ++ i) /// how much we delete from the front
    {
        int lastj = dp0[i+1];
        int firsti = dp1[n - (x - i)];
        if(lastj > firsti)continue;
        if(cnt[firsti - 1] - cnt[lastj] >= k)return true;
    }
    return false;
}
void solve()
{
    int left = 0, right = n - 3*k, mid, ans = -1;
    while(left <= right)
    {
        mid = (left + right) / 2;
        if(check(mid))
        {
            ans = mid;
            left = mid + 1;
        }
        else right = mid - 1;
    }
    if(ans == -1)cout << -1 << endl;
    else cout << n - 3*k - ans << endl;
}
int main()
{
    speed();

    read();
    precompute();
    solve();
    return 0;
}

Compilation message (stderr)

ho_t2.cpp: In function 'void precompute()':
ho_t2.cpp:27:21: warning: comparison of integer expressions of different signedness: 'std::deque<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   27 |         if(q.size() > k)q.pop_front();
      |            ~~~~~~~~~^~~
ho_t2.cpp:29:21: warning: comparison of integer expressions of different signedness: 'std::deque<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   29 |         if(q.size() < k)dp0[i] = n+1;
      |            ~~~~~~~~~^~~
ho_t2.cpp:36:21: warning: comparison of integer expressions of different signedness: 'std::deque<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   36 |         if(q.size() > k)q.pop_front();
      |            ~~~~~~~~~^~~
ho_t2.cpp:38:21: warning: comparison of integer expressions of different signedness: 'std::deque<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   38 |         if(q.size() < k)dp1[i] = 0;
      |            ~~~~~~~~~^~~

• Subtask 1: 1 / 1
• Subtask 2: 12 / 12
• Subtask 3: 87 / 87