Submission #491991

#	Time	Username	Problem	Language	Result	Execution time	Memory
491991		clams	Balloons (CEOI11_bal)	C++17	100 / 100	208 ms	14880 KiB

bal

#pragma GCC optimize(3)
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using db = long double;
#define int long long

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    
    int n;
    cin >> n;
    
    vector<db> x(n + 1), r(n + 1);
    for(int i = 1; i <= n; i++) {
        cin >> x[i] >> r[i];
    }    
    
    // distance between centers of 2 balloons
    // sqrt(abs(x2 - x1)**2 + abs(r2 - r1)**2)
    
    // must be equal to (r1 + r2)
    // => (x2 - x1)**2 + abs(r2 - r1)**2 == (r1 + r2)**2
    // => (x2**2 + x1**2 - 2x1x2) + (r2**2 + r1**2 - 2r1r2) = r1**2 + r2**2 + 2r1r2
    // => (x2 - x1)**2 = 4r1r2
    // => r2 = ((x2 - x1)**2) / (4r1)
    
    vector<db> ans(n + 1);
    stack<pair<db, db>> st;
    
    for(int i = 1; i <= n; i++) {
        if(st.empty()) {
            st.push({x[i], r[i]});
            ans[i] = r[i];
            continue;
        }
        
        while(!st.empty()) {
            pair<db, db> cur = st.top();
            r[i] = min(r[i], (x[i] - cur.first) * (x[i] - cur.first) / (4 * cur.second));
            if(r[i] >= cur.second) st.pop();
            else break;
        }
        
        st.push({x[i], r[i]});
        ans[i] = r[i];
    } 
    
    for(int i = 1; i <= n; i++) {
        cout << fixed << setprecision(3) << ans[i] << '\n';
    }
}

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10