Submission #442813

#	Time	Username	Problem	Language	Result	Execution time	Memory
442813		zaneyu	Monochrome Points (JOI20_monochrome)	C++14	100 / 100	56 ms	3044 KiB

monochrome

/*input
16
WWWBWBBBBWWBWWBWWBBWWBBBWBBBWWBW
*/
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<int,null_type,less_equal<int>,rb_tree_tag,tree_order_statistics_node_update> indexed_set;
//order_of_key #of elements less than x
// find_by_order kth element
using ll=long long;
using ld=long double;
using pii=pair<int,int>;
#define f first
#define s second
#define pb push_back
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(int i=1;i<=n;i++)
#define FILL(n,x) memset(n,x,sizeof(n))
#define ALL(_a) _a.begin(),_a.end()
#define sz(x) (int)x.size()
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()),c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
const ll INF64=1e18+1;
const int INF=0x3f3f3f3f;
const int MOD=1e9+9;
const ld PI=acos(-1);
const ld eps=1e-3;
#define lowb(x) x&(-x)
#define MNTO(x,y) x=min(x,(__typeof__(x))y)
#define MXTO(x,y) x=max(x,(__typeof__(x))y)
inline ll mult(ll a,ll b){
    if(a>=MOD) a%=MOD;
    if(b>=MOD) b%=MOD;
    return (a*b)%MOD;
}
inline ll mypow(ll a,ll b){
    if(b<=0) return 1;
    ll res=1LL;
    while(b){
        if(b&1) res=mult(res,a);
        a=mult(a,a);
        b>>=1;
    }
    return res;
}
const int maxn=2e5+5;
const int maxlg=__lg(maxn)+2;
int n;
vector<int> v1,v2;
ll cnt(int a){
    ll cur=0;
    REP(i,n){
        int x=v1[i],y=v2[(i+a)%n];
        cur+=min(abs(x-y),2*n-abs(x-y))-1;
    }
    return cur/2;
}
int32_t main(){
    ios::sync_with_stdio(false),cin.tie(0);
    cin>>n;
    REP(i,2*n){
        char c;
        cin>>c;
        if(c=='B') v1.pb(i);
        else v2.pb(i);
    }
    ll a=cnt(0),b=cnt(n-1);
    ll ans=max(a,b);
    int l=1,r=n-2;
    if(a<b){    
        while(l<r){
            int mid=(l+r)/2;
            ll x=cnt(mid);
            if(x<=a){
                l=mid+1;
                continue;
            }
            ll y=cnt(mid+1);
            if(x<y) l=mid+1;
            else r=mid;
        }
        MXTO(ans,cnt(l));
    }
    else{
        while(l<r){
            int mid=(l+r)/2;
            ll x=cnt(mid);
            if(x<=b){
                r=mid-1;
                continue;
            }
            ll y=cnt(mid+1);
            if(x<y) l=mid+1;
            else r=mid;
        }
        MXTO(ans,cnt(l));
    }
    cout<<ans;
}  

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