Line Intersections

// ~/.vim/cpp_template.cpp
#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <limits>

#define REP(i,a,b) for (int i = a; i < b; i++)

// Type Aliases for 1D and 2D vectors with initialization
#define vi(n, val) vector<int>(n, val) // 1D vector of ints with size n, initialized to val
#define vll(n, val) vector<long long>(n, val) // 1D vector of long longs with size n, initialized to val
#define ll long long
#define vvi(n, m, val) vector<vector<int>>(n, vector<int>(m, val)) // 2D vector of ints (n x m), initialized to val
#define vvll(n, m, val) vector<vector<long long>>(n, vector<long long>(m, val)) // 2D vector of long longs (n x m), initialized to val

#define LL_INF std::numeric_limits<long long int>::max()
#define INF std::numeric_limits<int>::max()


using namespace std;


template <typename T>
void pV(const std::vector<T>& vec, const std::string& label = "Vector") {
    std::cout << label << ": [ ";
    for (const auto& elem : vec) {
        std::cout << elem << " ";
    }
    std::cout << "]" << std::endl;
}


void dfs(int s, vector<bool> *visited, vector<int> (*adj)[]) {
    if ((*visited)[s]) return;
    (*visited)[s] = true;
    // process node s


    for (auto u: (*adj)[s]) {
        dfs(u, visited, adj);
    }
}
/*
// DEPTH-FRIRST-SEARCH
vector<int> adj[N];                                                          
vector<bool> visited(N, false);
int u, v;
for(int i = 0; i < M;i++){
    cin >> u >> v;
    u--;
    v--;
    adj[u].push_back(v);
    adj[v].push_back(u);
}
*/

vector<long long> dijkstra(int N, int x, vector<vector<pair<int,int>>> *adj){
    vector<bool> processed(N, false);
    vector<long long> distance(N, LL_INF);
    priority_queue<pair<long long,int>> q;
    //for (int i = 1; i <= n; i++) distance[i] = INF;
    distance[x] = 0;
    q.push({0,x});
    while (!q.empty()) {
        int a = q.top().second; q.pop();
        if (processed[a]) continue;
        processed[a] = true;
        for (auto u : (*adj)[a]) {
            int b = u.first, w = u.second;
            if (distance[a]+w < distance[b]) {
                distance[b] = distance[a]+w;
                q.push({-distance[b],b});
            }
        }
    }
    return distance;


}


/*
DIJKSTRA
//vector<vector<pair<int,int>>> adj(N, vector<pair<int, int>>(N));
*/


class SegmentTree {
private:
    vector<int> tree;
    int n;

public:
    SegmentTree(const vector<int>& arr) {
        n = arr.size();
        tree.resize(2 * n);

        for (int i = 0; i < n; i++) {
            tree[n + i] = arr[i];
        }
        for (int i = n - 1; i > 0; i--) {
            tree[i] = tree[2 * i] + tree[2 * i + 1];
        }
    }

    int sum(int a, int b) {
        a += n; b += n;
        int s = 0;
        while (a <= b) {
            if (a % 2 == 1) s += tree[a++];
            if (b % 2 == 0) s += tree[b--];
            a /= 2; b /= 2;
        }
        return s;
    }

    void set(int k, int x) {
        k += n;
        tree[k] = x;
        for (k /= 2; k >= 1; k /= 2) {
            tree[k] = tree[2 * k] + tree[2 * k + 1];
        }
    }

    void add(int k, int x) {
        k += n;
        tree[k] += x;
        for (k /= 2; k >= 1; k /= 2) {
            tree[k] = tree[2 * k] + tree[2 * k + 1];
        }
    }

    void sub(int k, int x) {
        k += n;
        tree[k] -= x;
        for (k /= 2; k >= 1; k /= 2) {
            tree[k] = tree[2 * k] + tree[2 * k + 1];
        }
    }

    void prnt(){
        pV(tree);
    }
};


const int HORSTART = 1;
const int HOREND = 2;
const int VERTICAL = 0;

struct Event {
    int x, y1, y2, type;
    Event(int x_, int y1_, int y2_, int type_) : x(x_), y1(y1_), y2(y2_), type(type_) {}
};

bitset<1000000> buildBitset(int a, int b){
    bitset<1000000> res;
    for (int i = a; i <= b; ++i) {
        res.set(i);
    }
    return res;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    // Your code starts here
    int n;
    cin >> n;

    vector<Event> events;
    vector<int> all_y_coords;

    REP(i, 0, n){
        int x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;

        if(y1 == y2) {
            if(x1 > x2) swap(x1, x2);
            events.emplace_back(x1, y1, y1, HORSTART);
            events.emplace_back(x2, y1, y1, HOREND);
            all_y_coords.push_back(y1);
        } else if(x1 == x2) {
            if(y1 > y2) swap(y1, y2);
            events.emplace_back(x1, y1, y2, VERTICAL);
            all_y_coords.push_back(y1);
            all_y_coords.push_back(y2);
        }
    }


    sort(all_y_coords.begin(), all_y_coords.end());
    all_y_coords.erase(unique(all_y_coords.begin(), all_y_coords.end()), all_y_coords.end());

    auto compress = [&](int y) {
        return lower_bound(all_y_coords.begin(), all_y_coords.end(), y) - all_y_coords.begin();
    };

    vector<int> arr(2*n+10, 0);
    SegmentTree segTree(arr);

    sort(events.begin(), events.end(), [](const Event& a, const Event& b) {
        if(a.x != b.x) return a.x < b.x;
        return a.type < b.type;
    });

    // process events
    long long intersections = 0;
    long long dhc = 0;
    int last_x = 0;
    bitset<1000000> seta, dble;

    for (const Event& event : events) {
        if(event.x - last_x>1){
            intersections+= (event.x-last_x) *dhc;
        }
        //segTree.prnt();
        //cout << event.type << " " << event.x << " " << event.y1 << " " << event.y2 << " " << dhc << endl;
        //cout << segTree.sum(compress(event.y1), compress(event.y1)) << endl;

        int curr= segTree.sum(compress(event.y1), compress(event.y1));
        if (event.type == HORSTART) {
            if(curr == 1){
                dhc++;
            }
            segTree.add(compress(event.y1), 1);
        }
        else if (event.type == HOREND) {
            if(curr == 2){
                dhc--;
            }
            segTree.sub(compress(event.y1), 1);
        }
        else if (event.type == VERTICAL) {
            intersections += segTree.sum(compress(event.y1), compress(event.y2));

            // handle vertical line intersection
            bitset<1000000> temp = buildBitset(compress(event.y1), compress(event.y2));
            if(event.x == last_x){
                dble = dble | (seta & temp);
                seta = seta | temp;
            }else{
                //intersections += __builtin_popcount(dble.to_ulong());
                intersections += dble.count();
                seta.reset();
                dble.reset();
                seta = seta | temp;
            }
        }
        intersections += dhc;
        last_x = event.x;
    }
    intersections+= dble.count();

    cout << intersections << endl;

    

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: WRONG ANSWER

Test 7

Verdict: ACCEPTED

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: ACCEPTED

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: WRONG ANSWER

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: ACCEPTED

Test 15

Verdict: WRONG ANSWER

Test 16

Verdict: WRONG ANSWER

Test 17

Verdict: WRONG ANSWER

Test 18

Verdict: WRONG ANSWER

Test 19

Verdict: WRONG ANSWER

Test 20

Verdict: WRONG ANSWER

Test 21

Verdict: WRONG ANSWER

Test 22

Verdict: WRONG ANSWER

Test 23

Verdict: WRONG ANSWER

Test 24

Verdict: WRONG ANSWER

Test 25

Verdict: WRONG ANSWER

Test 26

Verdict: WRONG ANSWER

Test 27

Verdict: WRONG ANSWER

Test 28

Verdict: WRONG ANSWER

Test 29

Verdict: WRONG ANSWER

Test 30

Verdict: WRONG ANSWER

Test 31

Verdict: WRONG ANSWER

Test 32

Verdict: WRONG ANSWER

Test 33

Verdict: WRONG ANSWER

Test 34

Verdict: WRONG ANSWER

Test 35

Verdict: WRONG ANSWER

Test 36

Verdict: WRONG ANSWER

Test 37

Verdict: WRONG ANSWER

Test 38

Verdict: WRONG ANSWER

Test 39

Verdict: WRONG ANSWER

Test 40

Verdict: WRONG ANSWER