Submission #493272

#	Time	Username	Problem	Language	Result	Execution time	Memory
493272		CraniXort	Mobile (BOI12_mobile)	C++17	4 / 100	918 ms	31552 KiB

mobile

#include <bits/stdc++.h>

#define maxn 100005
long double delta = 0.000001;

#define fin std::cin
#define fout std::cout

std::vector <std::pair <long double, long double>> v;


bool check(long double lenght, long double l) {
    long double left = -123, right = -123;
    for(auto i: v) {
        if(l*l - i.second * i.second < 0)
            continue;
        long double r = sqrtl(l*l - i.second * i.second);

        if(left == -123 and right == -123) {
            right = i.first + r;
            left = i.first - r;
            continue;
        }

        if(right >= i.first - r) {
            right = std::max(right, i.first + r);
            left = std::min(left, i.first - r);
        }
    }
    if(left <= 0 and right >= lenght)
        return true;
    return false;
}

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(NULL);
    std::cout.tie(NULL);

    int n;
    long double lenght;
    fin >> n >> lenght;
    v.resize(n);

    for(int i = 0; i < n; i ++)
        fin >> v[i].first >> v[i].second;

    long double left = 0, right = 2e9, mid, ans = 0;

    while(right - left >= delta) {
        mid = (left + right) / 2;

        if(check(lenght, mid) == true) {
            ans = mid;
            right = mid - delta;
        }
        else
            left = mid + delta;
    }

    fout << ans << '\n';
   
    return 0;
}

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