Submission #838829

#	Time	Username	Problem	Language	Result	Execution time	Memory
838829		a5a7	Mobile (BOI12_mobile)	C++14	0 / 100	1082 ms	62856 KiB

mobile

#include <bits/stdc++.h>
#define ALL(x) (x).begin(), (x).end()
#define REP(i, a, b) for (int i = (a); i < (b); i++)
#define READ(arr, n) for (int i = 0; i < (n); i++) cin >> arr[i];
#define ABS(a) (max((a), -(a)))
#define MOD 1000000007
using namespace std;
typedef long long ll;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n; long double l;
    cin >> n >> l;
    long double x[n];
    long double y[n];
    for (int i = 0; i < n; i++) cin >> x[i] >> y[i];
    long double left = 0;
    long double right = l;
    while ((right-left) > (0.0005)){
        long double mid = (left+right)/2;
        bool coversAll = true;
        pair<long double, long double> ranges[n];
        for (int i = 0; i < n; i++){
            long double sqr = sqrt(max(mid*mid-y[i]*y[i], (long double) 0));
            ranges[i].first = x[i]-sqr;
            ranges[i].second = x[i]+sqr;
        }
        sort(ranges, ranges+n);
        bool firstWork = true;
        for (int i = 0; i < (n-1) && coversAll; i++){
            if (ranges[i].second < 0) continue;
            if (ranges[i+1].first > l){
                if (ranges[i].second < l) coversAll = false;
                break;
            }
            if (firstWork){
                if (ranges[i].first > 0) coversAll = false;
                firstWork = false;
            }
            if (ranges[i].second < ranges[i+1].first) coversAll = false;
        }
        if (coversAll){
            right = mid;
        }else{
            left = mid;
        }
    }
    cout << left << endl;
}

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