Submission #1051965

#	Time	Username	Problem	Language	Result	Execution time	Memory
1051965		fryingduc	JJOOII 2 (JOI20_ho_t2)	C++17	100 / 100	6 ms	3924 KiB

ho_t2

#include "bits/stdc++.h"
using namespace std;

const int maxn = 2e5 + 5;
int n, k, a[maxn], pref[maxn], suf[maxn];
int ps[maxn];

string s;

void solve() {
    cin >> n >> k >> s;
    s = ' ' + s;
    vector<int> lst;
    for(int i = 1; i <= n; ++i) {
        ps[i] = ps[i - 1] + (s[i] == 'O');
        if(s[i] != 'J') continue;
        lst.push_back(i);
        pref[i] = -1;
        if((int)lst.size() < k) continue;
        int pos = lst[(int)lst.size() - k];
        
        pref[i] = (i - pos - k + 1);
    }
    lst.clear();
    memset(suf, 0x3f, sizeof(suf));
    for(int i = n; i; --i) {
        if(s[i] == 'I') {
            lst.push_back(i);
            if((int)lst.size() >= k) {
                int pos = lst[(int)lst.size() - k];
                suf[i] = (pos - k + 1);
            }
        }
    }
    for(int i = n - 1; i; --i) {
        suf[i] = min(suf[i], suf[i + 1]);
    }
    int ans = 1e9;
    for(int i = 1; i <= n; ++i) {
        if(s[i] != 'J' || pref[i] < 0) continue;
        int x = lower_bound(ps + 1, ps + n + 1, ps[i] + k) - ps;
        if(x > n) continue;
        ans = min(ans, (x - i - k) + pref[i] + suf[x + 1] - x - 1);
    }
    
    cout << (ans == 1e9 ? -1 : ans);
}
signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    
    solve();
    return 0;
}

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