Submission #54942

#	Time	Username	Problem	Language	Result	Execution time	Memory
54942		paulica	Printed Circuit Board (CEOI12_circuit)	C++14	30 / 100	317 ms	8964 KiB

circuit

#include <bits/stdc++.h>
using namespace std;

#define _ << " _ " <<
#define TRACE(x) cout << #x << " = " << x << endl

#define fi first
#define se second
typedef pair<int, int> pii;
typedef long long ll;
typedef long double ld;

const int MaxN = 1e5 + 10;

int n, x[MaxN], y[MaxN];
pair<int, int> line[MaxN];

ll ccw(int i, int j, int k) {
    return (ll)x[i] * (y[j] - y[k]) +
           (ll)x[j] * (y[k] - y[i]) +
           (ll)x[k] * (y[i] - y[j]);
}

ll dist(int i) {
    return (ll)x[i] * x[i] + (ll)y[i] * y[i];
}

bool equ(int i, int j) {
    return (ll)y[i] * x[j] == (ll)y[j] * x[i];
}

bool pointCmp(int i, int j) {
    if (equ(i, j)) return dist(i) < dist(j);
    return (ll)y[i] * x[j] < (ll)y[j] * x[i];
}

bool eventCmp(pair<pii, int>& a, pair<pii, int>& b) {
    if (equ(a.fi.fi, b.fi.fi) && a.se != b.se) return a.se < b.se;
    return pointCmp(a.fi.fi, b.fi.fi);
}

void printLine(int i) {cout << line[i].fi + 1 << "-" << line[i].se + 1 << " ";}

ld intersec(int i, int j) {
    int a = line[j].fi, b = line[j].se;

    if (x[a] == x[b]) return x[a];

    ld k1 = (ld)y[i] / x[i];
    ld k2 = (ld)(y[a] - y[b]) / (x[a] - x[b]);
    ld l = (ld)((ll)x[a] * y[b] - (ll)x[b] * y[a]) / (x[a] - x[b]);

    if (k1 - k2 == 0) return min(x[a], x[b]);

    /*
    cout << "intersec " << i + 1 << " ";
    printLine(j);
    cout << l / (k1 -k2) << endl;
    */
    
    return l / (k1 - k2);
}//*/

bool above(int i, int j) {
   // return ccw(line[j].fi, i, line[j].se) > 0;
    if (i == line[j].fi || i == line[j].se) return false;
    return intersec(i, j) < (ld)x[i];
}

int mod(int i) {
    if (i >= n) return i - n;
    return i;
}

struct lineCmp {
    bool operator()(int i, int j) {
        if (i == j) return false;

        bool ret;

        //cout << line[i].se + 1 << " " << line[j].se + 1 << " " << pointCmp(line[i].se, line[j].se) << endl;

        int a1 = line[i].fi, b1 = line[i].se;
        int a2 = line[j].fi, b2 = line[j].se;

        if ((mod(i + 1) == j))
            ret = x[i] < x[mod(i + 2)];
        else if ((mod(j + 1) == i)) 
            ret = x[mod(i + 1)] < x[j];
/*        else if (pointCmp(line[i].se, line[j].se)) {
            cout << "!!!\n";
            ret = above(line[j].fi, i);
        }
        else
            ret = above(line[j].se, i);
            */
/*        else {
            ld min1 = min(intersec(line[j].fi, i), intersec(line[j].se, i));
            ld min2 = min(intersec(line[i].fi, j), intersec(line[i].se, j));

            ret = min1 < min2;
        }
        */
        else if (pointCmp(a1, a2) && pointCmp(a2, b1))
            ret = above(a2, i);
        else if (pointCmp(a1, b2) && pointCmp(b2, b1))
            ret = above(b2, i);
        else if (pointCmp(a2, a1) && pointCmp(a1, b2))
            ret = !above(a1, j);
        else if (pointCmp(a2, b1) && pointCmp(b1, b2))
            ret = !above(b2, j);

        /*
        cout << "cmp ";
        printLine(i);
        printLine(j);
        cout << ret << endl << endl;
        cin.get();
        */
        return ret;
    }
};

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    cin >> n;

    vector<pair<pii, int>> events;

    for (int i = 0; i < n; i++) {
        cin >> x[i] >> y[i];
        events.push_back({{i, i}, 1});
    }
    
    for (int i = 0; i < n; i++) {
        if (i == n - 1) line[i] = {i, 0};
        else line[i] = {i, i + 1};
        
        if (pointCmp(line[i].se, line[i].fi))
            swap(line[i].fi, line[i].se);

        events.push_back({{line[i].fi, i}, 0});
        events.push_back({{line[i].se, i}, 2});
    }
    
   // lineCmp c;
    //cout << c(6, 8) << endl;

    sort(events.begin(), events.end(), eventCmp);

    set<int, lineCmp> lines;

    vector<int> sol;

    for (auto ev : events) {
        if (ev.se == 0) {
            lines.insert(ev.fi.se);
            //int l = ev.fi.se;
            //cout << "+ ";
            //printLine(l);
            //cout << endl;
        } else if (ev.se == 1) {
            int i = ev.fi.se;
//            cout << endl;
  //          TRACE(i + 1);
    //        for (int l : lines) cout << line[l].fi + 1 << "-" << line[l].se + 1  << " "; cout << endl;
            int j = *lines.begin();
      //      cout << line[j].fi + 1 << "-" << line[j].se + 1 << endl;

 //           if (intersec(i, j) >= x[i]) 
            if (!above(i, j)) sol.push_back(i);
          //  if (!above(i, j)) cout << "yes\n";
        //    cout << endl;
        } else {
    //        cout << "!" << (lines.find(ev.fi.se) != lines.end()) << "!\n";
      //      cout << lines.size() << " -> ";
            lines.erase(ev.fi.se);
        //    cout << lines.size() << "  ";
           // cout << "- ";
          //  printLine(ev.fi.se);
        //    cout << "   " << ev.fi.se << endl;
        }
    }

    sort(sol.begin(), sol.end());

    cout << sol.size() << "\n";
    for (int i : sol) cout << i + 1 << " ";

    return 0;
}

Compilation message (stderr)

circuit.cpp: In member function 'std::pair<std::_Rb_tree_iterator<_Val>, bool> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_unique(_Arg&&) [with _Arg = const int&; _Key = int; _Val = int; _KeyOfValue = std::_Identity<int>; _Compare = lineCmp; _Alloc = std::allocator<int>]':
circuit.cpp:79:14: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
         bool ret;
              ^~~

• Subtask 1: 30 / 100