Submission #466651

#	Time	Username	Problem	Language	Result	Execution time	Memory
466651		bill_lin	Mobile (BOI12_mobile)	C++14	100 / 100	618 ms	22428 KiB

mobile

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
using namespace std;
 
#define MOD 1000000007
#define INF 10000000

int n, l;

vector<pii> coords;

bool possible(ld curr) {
    ld right_bound = 0;
    for (int i = 0; i < n; i++) {
        if ((ld) coords[i].second * coords[i].second > curr * curr) continue;
        ld left_most = coords[i].first - sqrt(curr * curr - (ld) coords[i].second * coords[i].second);
        if (left_most <= right_bound) right_bound = max(right_bound, coords[i].first + sqrt(curr * curr - (ld) coords[i].second * coords[i].second));
        
    }
    return right_bound <= l;
}

int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
//    freopen("multimoo.in", "r", stdin);
//    freopen("multimoo.out", "w", stdout);
    
    cin >> n >> l;
    
    coords.resize(n);
    for (int i = 0; i < n; i++) {
        int x, y;
        cin >> x >> y;
        coords[i] = {x, y};
    }
    
    ld l = 0, r = 1000000000;
    for (int iteration = 0; iteration <= 50; iteration++) {
        ld mp = (l + r) / 2;
        if (possible(mp)) {
            l = mp;
        } else r = mp;
    }
    
    cout.precision(6);
    cout << fixed << l << '\n';
    
}

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