Submission #3471572

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Source Code Expand

#include <bits/stdc++.h>

using namespace std;
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
constexpr int dx[] = {1, 0, -1, 0, 1, 1, -1, -1};
constexpr int dy[] = {0, -1, 0, 1, 1, -1, -1, 1};

template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec){os << "["; for (const auto &v : vec) {os << v << ","; } os << "]"; return os; }
template <typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &p) {os << "(" << p.first << ", " << p.second << ")"; return os;}

double len(int x1, int y1, int x2, int y2) {
    return sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
}

void solve() {
    double x1, y1, x2, y2, x3, y3;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    double a = len(x1, y1, x2, y2);
    double b = len(x2, y2, x3, y3);
    double c = len(x3, y3, x1, y1);

    double s = (a + b + c) / 2;
    double S = sqrt(s * (s - a) * (s - b) * (s - c));
    // (a + b + c) * r / 2 == S
    // r = S * 2 / (a + b + c)
    double r = 2 * S / (a + b + c);
    double m = max({a, b, c});
    // (1 - x/r) * m == 2x
    // m - (m/r) x - 2x = 0
    // m = (m/r + 2)x
    // x = m / (m/r + 2)

    double x = m / ((m / r) + 2);
    cout << x << endl; 
}

int main() {
    std::cin.tie(0);
    std::ios::sync_with_stdio(false);
    cout.setf(ios::fixed);
    cout.precision(16);
    solve();
    return 0;
}

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