제출 #483711

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
483711		sam571128	Geometrija (COCI21_geometrija)	C++17	20 / 110	1088 ms	1584 KiB

geometrija

#include <bits/stdc++.h>

#define int long long
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

using namespace std;

typedef pair<int,int> point;
#define x first
#define y second

int operator^(point a, point b){
    return a.x*b.y-a.y*b.x;
}

int operator*(point a, point b){
    return a.x*b.x+a.y*b.y;
}

point operator-(point a, point b){
    return {a.x-b.x,a.y-b.y};
}

point operator+(point a, point b){
    return {a.x+b.x,a.y+b.y};
}

int ori(point a, point b, point c){
    int tmp = (b-a)^(c-a);
    if(tmp == 0) return 0;
    return abs(tmp)/tmp;
}
int intersect(point a, point b, point c, point d){
    int abc = ori(a,b,c);
    int abd = ori(a,b,d);
    int cda = ori(c,d,a);
    int cdb = ori(c,d,b);

    if(abc*abd < 0 && cda*cdb < 0) return true;
    else return false;
}

signed main(){
    fastio
    
    int n;
    cin >> n;
    vector<point> arr;
    for(int i = 0;i < n;i++){
        int a,b;
        cin >> a >> b;
        arr.push_back({a,b});
    }

    int ans = n*(n-1)/2;
    map<point,int> m;
    for(int a = 0; a < n; a++){
        for(int b = a+1; b < n; b++){
            for(int c = 0; c < n; c++){
                for(int d = c+1; d < n; d++){
                    if(intersect(arr[a],arr[b],arr[c],arr[d])){
                        m[{a,b}]++;
                        m[{c,d}]++;
                    }
                }
            }
        }
    }
    cout << ans-m.size() << "\n";
}

• Subtask 1: 20 / 20
• Subtask 2: 0 / 30
• Subtask 3: 0 / 60