Submission #751043

#	Time	Username	Problem	Language	Result	Execution time	Memory
751043		ToniB	Monochrome Points (JOI20_monochrome)	C++17	25 / 100	2086 ms	304 KiB

monochrome

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 4e5 + 2;

int n;
string s;
vector<int> white, black;

bool cross(int x1, int y1, int x2, int y2){
    if(x1 > y1) swap(x1, y1);
    if(x2 > y2) swap(x2, y2);
    if(x1 < x2 && y2 < y1) return false;
    if(x2 < x1 && y1 < y2) return false;
    if(x1 > y2 || x2 > y1) return false;
    return true;
}

int calc(int delta){
    int ret = 0;
    for(int i = 0; i < n; ++i){
        for(int j = i + 1; j < n; ++j){
            if(cross(white[i], black[(i + delta) % n], white[j], black[(j + delta) % n])) ++ret;
        }
    }
    return ret;
}

int main(){
    cin >> n >> s;

    for(int i = 0; i < 2*n; ++i){
        if(s[i] == 'W') white.push_back(i);
        else black.push_back(i);
    }

    int ans = 0;
    for(int i = 0; i < n; ++i){
        ans = max(ans, calc(i));
    }

    cout << ans;
	return 0;
}

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