Submission #1095896

#	Time	Username	Problem	Language	Result	Execution time	Memory
1095896		_8_8_	Monochrome Points (JOI20_monochrome)	C++17	35 / 100	2041 ms	11852 KiB

monochrome

#include <bits/stdc++.h>
    
using namespace std;
    
typedef long long ll;
const int  N = 3e5 + 12, MOD = (int)1e9 + 7;

int n, t[N * 2];
string s;
vector<int> x, y;

void add(int i, int val) {
    while(i <= n + n) {
        t[i] += val;
        i += i & -i;
    }
}
ll get(int i) {
    ll ret = 0;
    while(i) {
        ret += t[i];
        i -= i & -i;
    }
    return ret;
}
ll get(int l, int r) {
    return get(r) - get(l - 1);
}
ll calc(int k) {
    for(int i = 1; i <= n + n; i++) {
        t[i] = 0;
    }
    ll ret = 0;
    vector<pair<int,int>> a;
    for(int i = 0; i < n; i++) {
        int j = (i + k) % n;
        int l = x[i], r = y[j];
        if(l > r) {
            swap(l, r);
        }
        a.emplace_back(l, -1);
        a.emplace_back(r, l);
    }
    // return 0;
    sort(a.begin(), a.end());
    for(auto [x, y]:a) {
        if(y == -1) {
            add(x, 1); 
        } else {
            ret += get(y + 1, x);
            add(y, -1);
        }
    }
    return ret;
}
void test() {
    cin >> n >> s;
    for(int i = 0; i < n + n; i++) {
        if(s[i] == 'W') {
            x.push_back(i + 1);
        } else {
            y.push_back(i + 1);
        }
    }
    ll res = 0;
    for(int i = 0; i < n; i++) {
        // cout << i << ' ' << calc(i) << '\n';
        res = max(res, calc(i));
    }
    cout << res << '\n';
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0); 

    int t = 1; 
    // cin >> t;
    
    while(t--) 
        test();
    return 0;
}

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