Submission #658004

#	Time	Username	Problem	Language	Result	Execution time	Memory
658004		chjiao	Mobile (BOI12_mobile)	C++14	100 / 100	478 ms	31444 KiB

mobile

//Binary search the shortest length from the firehose
 
#include <bits/stdc++.h>
using namespace std;
 
#define fastio	ios_base::sync_with_stdio(false);cin.tie(0)
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
 
#define FOR(i,a,b) for(ll i=a;i<=b;i++)
#define FORB(i,a,b) for(ll i=a;i>=b;i--)
 
#define getbit(mask,i) ((mask>>(i))&1)
#define getnum(i) (1<<(i))
 
#define endl "\n"
#define sz(x) (int)size(x)
#define mp make_pair
using ll = long long;
const ll MOD1 = 1e9+7;
const ll MOD2 = 998244353;
const ll MN = 1e5;
const ll MAX = LLONG_MAX;
long double FLOAT_ERR = 1e-5;
long double first_true_float(long double lo, long double hi, function<bool(long double)> f) {
	// if none of the values in the range work, return hi + 1
	lo--;
	hi++;
	while (hi-lo > FLOAT_ERR) {
		long double mid =  (lo + hi) / 2.0f;
		if (f(mid)) {
			hi = mid;
		} else {
			lo = mid;
		}
	}
	return lo;
}
 
int main() {
    fastio;
	// freopen("XXX.in","r",stdin);
	// freopen("XXX.out","w",stdout);
    ll N;
    ll L;
    cin >> N >> L;
    vector<pair<ll,ll>> input(N);
    for(int i=0; i<N; i++){
        cin >> input[i].first >> input[i].second;
    }
    // sort(input.begin(), input.end());
    cout << fixed << setprecision(6)<<first_true_float(1, 1.5e9, [&](long double x){
        long double left = 0;
        for(auto cell:input){
            if(x*x < cell.second*cell.second){
                continue;
            }
            long double diviation = sqrt(x*x - cell.second*cell.second);
        
            if((cell.first-diviation) <= left){
                left =max(left, cell.first+diviation);
            } 
        }
        return left >= L;

    }) << endl;
}

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
• Subtask 3: 4 / 4
• Subtask 4: 4 / 4
• Subtask 5: 4 / 4
• Subtask 6: 5 / 5
• Subtask 7: 5 / 5
• Subtask 8: 5 / 5
• Subtask 9: 5 / 5
• Subtask 10: 5 / 5
• Subtask 11: 5 / 5
• Subtask 12: 5 / 5
• Subtask 13: 5 / 5
• Subtask 14: 5 / 5
• Subtask 15: 5 / 5
• Subtask 16: 5 / 5
• Subtask 17: 5 / 5
• Subtask 18: 5 / 5
• Subtask 19: 5 / 5
• Subtask 20: 5 / 5
• Subtask 21: 5 / 5