Submission #332699

#	Time	Username	Problem	Language	Result	Execution time	Memory
332699		limabeans	JJOOII 2 (JOI20_ho_t2)	C++17	100 / 100	35 ms	4056 KiB

ho_t2

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

template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl





using ll = long long;


const int maxn = 1e6 + 5;




int n,k;
string s;
int a[maxn];
int acc[maxn][3];

int main() {
    ios_base::sync_with_stdio(false); cin.tie(0);  cout.tie(0);

    cin>>n>>k;
    cin>>s;
    for (int i=0; i<n; i++) {
	if (s[i]=='J') {
	    a[i+1]=0;
	} else if (s[i]=='O') {
	    a[i+1]=1;
	} else if (s[i]=='I') {
	    a[i+1]=2;
	} else assert(false);
    }

    for (int i=1; i<=n; i++) {
	acc[i][a[i]]++;
	for (int j=0; j<3; j++) {
	    acc[i][j] += acc[i-1][j];
	}
    }


    auto qry = [&](int l, int r, int i) {
	return acc[r][i] - acc[l-1][i];
    };


    int res = 2*n;

    for (int i=1; i<=n; i++) {
	if (a[i]==1) {
	    if (qry(1,i,0)<k || qry(i,n,1)<k || qry(1,n,2)<k) {
		continue;
	    }

	    int L = -1, R = -1;

	    // reach back for J
	    {
		int lo = 1;
		int hi = i+1;
		while (hi-lo>1) {
		    int mid=(lo+hi)/2;
		    if (qry(mid,i,0)>=k) {
			lo = mid;
		    } else {
			hi = mid;
		    }
		}

		L = lo;
	    }


	    int I = -1;
	    // find kth I
	    {
		int lo = i-1;
		int hi = n;
		while (hi-lo>1) {
		    int mid=(lo+hi)/2;
		    if (qry(i,mid,1)>=k) {
			hi = mid;
		    } else {
			lo = mid;
		    }
		}

		I = hi;
	    }

	    if (qry(I,n,2)<k) {
		continue;
	    }

	    // find kth O
	    {
		int lo = I-1;
		int hi = n;
		while (hi-lo>1) {
		    int mid=(lo+hi)/2;
		    if (qry(I,mid,2)>=k) {
			hi = mid;
		    } else {
			lo = mid;
		    }
		}

		R = hi;
	    }

	    // watch(i);
	    // cout<<L<<" "<<I<<" "<<R<<endl;
	    int cur = (R-L+1) - 3*k;
	    res = min(res, cur);
	}
    }
    

    if (res>n) res=-1;
    cout<<res<<endl;
    
    return 0;
}

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