verify/geometry/aoj-cgl-3-a.test.cpp

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• Last update: 2024-08-09 13:11:28+00:00
• Problem: https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_3_A

Depends on

• contest/template.cpp
• geometry/Point.cpp

Code

#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_3_A"
#define ERROR 0.00000001


#define main main2
#include "../../contest/template.cpp"
#undef main

#include "../../geometry/Point.cpp"

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cout.precision(20), cout.setf(ios::fixed);

    int n;
    cin >> n;
    vector<vec> arr(n);
    for (auto &el : arr) {
        cin >> el.x >> el.y;
    }
    ld res = 0;
    for (int i = 0; i < n; ++i) {
        auto a = arr[i];
        auto b = arr[i + 1 < n ? i + 1 : 0];
        res += a % b;
        // res += arr[i] % arr[(i + 1) ? (i + 1 < n) : 0];
    }
    res /= 2;
    res = abs(res);
    cout << setprecision(1) << res << '\n';
    cout << endl;
}

#line 1 "verify/geometry/aoj-cgl-3-a.test.cpp"
#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_3_A"
#define ERROR 0.00000001


#define main main2
#line 1 "contest/template.cpp"
#ifdef LOCAL
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using ld = long double;
using ull = unsigned long long;

#define pbc push_back
#define mp make_pair
#define all(v) (v).begin(), (v).end()
#define vin(v) for (auto &el : a) cin >> el

mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());

template <typename T1, typename T2> inline void chkmin(T1 &x, const T2 &y) {
    if (y < x) {
        x = y;
    }
}

template <typename T1, typename T2> inline void chkmax(T1 &x, const T2 &y) {
    if (x < y) {
        x = y;
    }
}

void solve() {
    
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cout.precision(20), cout.setf(ios::fixed);
    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }
}
#line 7 "verify/geometry/aoj-cgl-3-a.test.cpp"
#undef main

#line 1 "geometry/Point.cpp"
/**
 * Author: alexxela12345,daubi,talant
 * Date: 2024-08-03
 * Description: struct Point
 */

const ld EPS = 1e-7;

ld sq(ld x) {
    return x * x;
}

int sign(ld x) {
    if (x < -EPS) {
        return -1;
    }
    if (x > EPS) {
        return 1;
    }
    return 0;
}

#define vec point
struct point {//% - cross, * - dot
    ld x, y;
    auto operator<=>(const point&) const = default;
};
ld operator*(const point &a, const point &b) {
    return a.x * b.x + a.y * b.y;
}
ld operator%(const point &a, const point &b) {
    return a.x * b.y - a.y * b.x;
}
point operator-(const point &a, const point &b) {
    return {a.x - b.x, a.y - b.y};
}
point operator+(const point &a, const point &b) {
    return {a.x + b.x, a.y + b.y};
}
point operator*(const point &a, ld b) {
    return {a.x * b, a.y * b};
}
point operator/(const point &a, ld b) {
    return {a.x / b, a.y / b};
}
bool operator<(const point &a, const point &b)  {
    if (sign(a.y - b.y) != 0) {
        return a.y < b.y;
    } else if (sign(a.x - b.x) != 0) {
        return a.x < b.x;
    }
    return 0;
}
ld len2(const point &a) {
    return sq(a.x) + sq(a.y);
}
ld len(const point &a) {
    return sqrt(len2(a));
}
point norm(point a) {
    return a / len(a);
}
int half(point a) {
    return (sign(a.y) == -1 || (sign(a.y) ==0 && a.x < 0));
}
point ort(point a) {
    return {-a.y, a.x};
}
point turn(point a, ld ang) {
    return {a.x * cos(ang) - a.y * sin(ang), a.x * sin(ang) + a.y * cos(ang)};
}
ld getAngle(point &a, point &b) {
    return atan2(a % b, a * b);
}
bool cmpHalf(const point &a, const point &b) {
    if (half(a) != half(b)) {
        return half(b);
    } else {
        int sgn = sign(a % b);
        if (!sgn) {
            return len2(a) < len2(b);
        } else {
            return sgn == 1;
        }
    }
}
#line 10 "verify/geometry/aoj-cgl-3-a.test.cpp"

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cout.precision(20), cout.setf(ios::fixed);

    int n;
    cin >> n;
    vector<vec> arr(n);
    for (auto &el : arr) {
        cin >> el.x >> el.y;
    }
    ld res = 0;
    for (int i = 0; i < n; ++i) {
        auto a = arr[i];
        auto b = arr[i + 1 < n ? i + 1 : 0];
        res += a % b;
        // res += arr[i] % arr[(i + 1) ? (i + 1 < n) : 0];
    }
    res /= 2;
    res = abs(res);
    cout << setprecision(1) << res << '\n';
    cout << endl;
}

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