Submission #545765

#	Time	Username	Problem	Language	Result	Execution time	Memory
545765		Koosha_mv	Monochrome Points (JOI20_monochrome)	C++14	100 / 100	378 ms	7428 KiB

monochrome

#include <bits/stdc++.h>
using namespace std;
#define dbgv(v) cout<<#v<<" = "; f(i,0,v.size()) cout<<v[i]<<" "; cout<<endl
#define dbga(a,x,y) cout<<#a<<" = "; f(i,x,y) cout<<a[i]<<" "; cout<<endl
#define erorp(x) cout<<#x<<"={"<<(x.F)<<" , "<<x.S<<"}"<<endl
#define eror(x) cout<<#x<<'='<<(x)<<endl
#define f_(i,a,b) for(int i=a;i>=b;i--)
#define f(i,a,b) for(int i=a;i<b;i++)
#define nb(x) __builtin_popcount(x)
#define all(v) v.begin(),v.end()
#define bit(n,k) (((n)>>(k))&1)
#define Add(x,y) x=(x+y)%mod
#define maxm(a,b) a=max(a,b)
#define minm(a,b) a=min(a,b)
#define lst(x) x[x.size()-1]
#define sz(x) int(x.size())
#define mp make_pair
#define ll long long
#define pb push_back
#define S second
#define F first

const int N=4e5+99;

int n,a[N],L[N],R[N],fenwik[N];
string s;
vector<int> vec0,vec1;

void add(int x, int val){ for (x++;x>0;x-=x&-x) fenwik[x]+=val; }
int get(int x) { int res=0; for(x++;x<N;x+=x&-x) res+=fenwik[x]; return res; }

ll calc(int shift){
	f(i,0,N) fenwik[i]=0;
	ll res=0;
	f(i,0,n){
		L[i]=min(vec0[i],vec1[(i+shift)%n]);
		R[i]=max(vec0[i],vec1[(i+shift)%n]);
		a[L[i]]=i;
		a[R[i]]=i;
	}
	f(i,0,2*n){
		if(L[a[i]]==i){
			add(i,1);
		}
		else{
			add(L[a[i]],-1);
			res+=get(L[a[i]]);
		}
	}
	return res;
}

int32_t main(){
	ios:: sync_with_stdio(0), cin.tie(0), cout.tie(0);
	cin>>n>>s;
	f(i,0,2*n) if(s[i]==s[0]) vec0.pb(i); else vec1.pb(i);
	int l=-1,r=n-1;
	while(l+1<r){
		int mid=(l+r)>>1;
		if(calc(mid)<calc(mid+1)){
			l=mid;
		}
		else{
			r=mid;
		}
	}
	cout<<calc(r);
}
                                   

• Subtask 1: 4 / 4
• Subtask 2: 21 / 21
• Subtask 3: 10 / 10
• Subtask 4: 65 / 65