Submission #951232

#	Time	Username	Problem	Language	Result	Execution time	Memory
951232		seriouslyFlawed	Mobile (BOI12_mobile)	C++17	0 / 100	1101 ms	21428 KiB

mobile

//#pragma GCC optimize("03,unroll-loops")

#include <bits/stdc++.h>

using namespace std;

// Shortcuts for common operations
#define pb push_back
#define p push
#define ppb pop_back
#define f first
#define s second
#define all(x) (x).begin(), (x).end()
#define ll long long
//#define int ll
#define endl "\n"
#define sz(x) (int)x.size()

// Type definitions for convenience
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<bool> vb;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<vi> vvi;
typedef vector<pii> vii;

// Debugging macros
#define debug(x) cerr << #x << " = " << (x) << '\n'
#define debug_vector(v) _debug_vector(#v, v)
template<typename T>
void _debug_vector(const string& name, const vector<T>& a) {
    cerr << name << " = [ ";
    for(const auto &x : a) cerr << x << ' ';
    cerr << "]\n";
}

// I/O redirection for local testing
#define iofile(io) \
        freopen((io + ".in").c_str(), "r", stdin); \
        freopen((io + ".out").c_str(), "w", stdout);

// delta for floodfill
vi dx = {0, 1, 0, -1};
vi dy = {1, 0, -1, 0};

// extended deltas for floodfill
vi edx = {0, 1, 0, -1, 1, 1, -1, -1};
vi edy = {1, 0, -1, 0, 1, -1, 1, -1};

// Common outputs
void yes() { cout << "YES" << '\n'; }
void no() { cout << "NO" << '\n'; }

#define ld long double
vii tab;
int n;
ld l;


bool check(ld alpha){
    stack<pair<ld, ld>>s;

    for(int i = 0; i < n; i++){
        auto [x, y] = tab[i];
        ld a = max(((ld)0), x - sqrt(alpha*alpha - y*y));
        ld b = min(l, x + sqrt(alpha*alpha - y*y));
        s.push({a, b});
        while(s.size() >= 2){
            auto [a, b] = s.top();
            s.pop();

            if(s.top().s >= a) s.top().f = max(((ld)0), min(s.top().f, a)), s.top().s = min(l, max(s.top().s, b));
            else{ s.push({a, b}); break; }
        }
    }

    return (s.size() == 1 and s.top().f == 0 and s.top().s == l);
}


void fx() {
    cin >> n >> l;

    for(int i = 0; i < n; i++){
        pii curr;
        cin >> curr.f >> curr.s;
        tab.pb(curr);
    }

    ld lo = 0;
    ld hi = 1e10; 
    ld eps = 1e-4;

    while(hi - lo > eps){
        ld mid = (lo + hi)/2;
        if(check(mid)) hi = mid;
        else lo = mid;
    }

    cout << lo << endl;

}

signed main() {

    cin.tie(0)->sync_with_stdio(0);
    // Uncomment the following lines for file I/O
    // iofile(string("hello"));
    
    // Uncomment the following lines for multiple test cases
    // int t; cin >> t; while(t--) fx();
    
    // Single test case
    fx();
    
    return 0;
}

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