Submission #617248

#	Time	Username	Problem	Language	Result	Execution time	Memory
617248		AmirElarbi	Monochrome Points (JOI20_monochrome)	C++14	100 / 100	40 ms	4960 KiB

monochrome

#include <bits/stdc++.h>
#define vi vector<int>
#define ve vector
#define ll long long
#define vf vector<float>
#define vll vector<pair<ll,ll>>
#define ii pair<int,int>
#define pll pair<ll,ll>
#define vvi vector<vi>
#define vii vector<ii>
#define gii greater<ii>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define INF 2e9+5
#define eps 1e-7
#define eps1 1e-25
#define optimise ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define MAX_A 1e5+5
#define V 450
using namespace std;
const int MOD = 1e9;
const int nax = 2e5+5;
const int lg = 20;
ll dp[nax];
int n;
vi blck, wht;
ll test(int md){
    if(dp[md] != -1) return dp[md];
    ll res = 0;
    for (int j = 0; j < n; ++j)
    {
        int ind = (j+md)%n;
        int a = blck[j], b = wht[ind];
        if(a > b) swap(a,b);
        int bt = b-a-1;
        res += min(bt, 2*n-bt-2);
    }
    res /= 2;
    return dp[md] = res;
}
int main() {
    optimise;
    cin >> n;
    string s;
    cin >> s;
    memset(dp, -1, sizeof dp);
    for (int i = 0; i < n*2; ++i)
    {
        if(s[i] == 'B') blck.pb(i);
        if(s[i] == 'W') wht.pb(i);
    }
    ll mx = 0;
    int l = 0, r = n;
    while (l < r)
    {
        int md = (l+r)/2;
        ll a = test(md+1), b = test(md);
        if(a > b){
            mx = max(mx, a);
            l = md+1;
        } else {
            mx = max(mx, b);
            r = md;
        }
    }
    cout << mx << '\n';
}

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