Submission #684717

#	Time	Username	Problem	Language	Result	Execution time	Memory
684717		alvingogo	Monochrome Points (JOI20_monochrome)	C++14	0 / 100	2081 ms	212 KiB

monochrome

#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define AquA cin.tie(0);ios_base::sync_with_stdio(0);
#define fs first
#define sc second
#define p_q priority_queue
#define int long long
using namespace std;

signed main(){
    AquA;
    int n;
    cin >> n;
    string s;
    cin >> s;
    int ans=1e14;
    vector<int> a,b;
    for(int i=0;i<n;i++){
        if(s[i]=='B'){
            a.push_back(i);
        }
        if(s[i+n]=='W'){
            b.push_back(i);
        }
    }
    int nn=n;
    n=a.size();
    vector<int> mp(n,-1);
    auto f=[&](int i){
        if(mp[i]>=0){
            return mp[i];
        }
        int xx=0;
        for(int j=0;j<n;j++){
            xx+=min(abs(b[j]-a[(i+j)%n]),nn-abs(b[j]-a[(i+j)%n]));
        }
        ans=min(ans,xx);
        mp[i]=xx;
        return xx;
    };
    int z;
    if(n){
        if(f(0)<f(n-1)){
            z=n-1;
            int l=0,r=n-1;
            while(r>l){
                int m=(l+r)/2;
                if(f(m)<=f(z)){
                    r=m;
                }
                else{
                    l=m+1;
                }
            }
            int bl=l,br=n-1;
            while(br>bl+1){
                int m=(bl+br)/2;
                if(f(m)>f(m+1)){
                    bl=m;
                }
                else{
                    br=m+1;
                }
            }
            f(bl);
            f(br);
        }
        else{
            z=0;
            int l=0,r=n-1;
            while(r>l){
                int m=(l+r+1)/2;
                if(f(m)<=f(z)){
                    l=m;
                }
                else{
                    r=m-1;
                }
            }
            int bl=0,br=l;
            while(br>bl+1){
                int m=(bl+br)/2;
                if(f(m)>f(m+1)){
                    bl=m;
                }
                else{
                    br=m+1;
                }
            }
            f(bl);
            f(br);
        }
    }
    else{
        ans=0;
    }
    cout << nn*(nn-1)/2-ans << "\n";
    return 0;
}

• Subtask 1: 0 / 4
• Subtask 2: 0 / 21
• Subtask 3: 0 / 10
• Subtask 4: 0 / 65