Submission #7975582

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Source Code Expand

// https://atcoder.jp/contests/abc002/tasks/abc002_3
#include <bits/stdc++.h>
using namespace std;
// #define int long long
#define REP(i, n) FOR(i, 0, n)
#define REPR(i, n) for (int i = n - 1; i >= 0; i--)
#define FOR(i, s, n) for (int i = (s), i##_len = (n); i < i##_len; ++i)
#define ALL(obj) (obj).begin(), (obj).end()
#define ALLR(obj) (obj).rbegin(), (obj).rend()
#define DIV(a, b) ((a - 1) / b + 1)

// ヘロンの公式
double areatri(double a, double b, double c) {
    double S = (a + b + c) / 2;
    return sqrt(S * (S - a) * (S - b) * (S - c));
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    vector<int> x(3), y(3);
    REP(i, 3) { cin >> x[i] >> y[i]; }
    // 3辺の長さ
    vector<double> dist;
    REP(i, 3) FOR(j, i + 1, 3) {
        dist.push_back(hypot(x[j] - x[i], y[j] - y[i]));
    }
    printf("%.9lf\n", areatri(dist[0], dist[1], dist[2]));

    return 0;
}

Submission Info

Judge Result