Add a bunch of other problems

Educational Codeforces Round 1/C. Nearest vectors.cpp

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+/* Problem URL: https://codeforces.com/contest/598/problem/C */
+
+#include <bits/stdc++.h>
+#include <ext/pb_ds/assoc_container.hpp>
+#include <ext/pb_ds/tree_policy.hpp>
+
+using namespace std;
+using namespace __gnu_pbds;
+
+template <class T, class comp = less<>>
+using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;
+
+#define V vector
+
+#define rmin(a, b) a = min(a, b)
+#define rmax(a, b) a = max(a, b)
+
+#define rep(i, lim) for (int i = 0; i < (lim); i++)
+#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
+
+#define repv(i, v) for (auto &i : (v))
+#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
+#define sortv(v) sort(v.begin(), v.end())
+#define all(v) (v).begin(), (v).end()
+
+using vi = vector<int>;
+using vvi = vector<vi>;
+using vvvi = vector<vvi>;
+using vvvvi = vector<vvvi>;
+
+using ll = long long;
+
+using vl = vector<ll>;
+using vvl = vector<vl>;
+using vvvl = vector<vvl>;
+using vvvvl = vector<vvvl>;
+
+template<class v>
+auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
+    os << vec[0];
+    for (size_t i = 1; i < vec.size(); i++) {
+        os << ' ' << vec[i];
+    }
+    os << '\n';
+    return os;
+}
+
+template<class v>
+auto operator>>(istream &is, vector<v> &vec)->istream& {
+    for (auto &i : vec) {
+        is >> i;
+    }
+    return is;
+}
+
+template<class v>
+auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
+    for (auto &i : vec) {
+        os << i[0];
+        for (size_t j = 1; j < i.size(); j++) {
+            os << ' ' << i[j];
+        }
+        os << '\n';
+    }
+    return os;
+}
+
+template<class v>
+auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
+    for (auto &i : vec) {
+        for (auto &j : i) {
+            is >> j;
+        }
+    }
+    return is;
+}
+
+#define sq(x) ((x)*(ll)(x))
+
+struct pt { // ponto
+	ll x, y;
+	pt(int x_ = 0, int y_ = 0) : x(x_), y(y_) {}
+	bool operator < (const pt p) const {
+		if (x != p.x) return x < p.x;
+		return y < p.y;
+	}
+	bool operator == (const pt p) const {
+		return x == p.x and y == p.y;
+	}
+	pt operator + (const pt p) const { return pt(x+p.x, y+p.y); }
+	pt operator - (const pt p) const { return pt(x-p.x, y-p.y); }
+	pt operator * (const int c) const { return pt(x*c, y*c); }
+	ll operator * (const pt p) const { return x*(ll)p.x + y*(ll)p.y; }
+	ll operator ^ (const pt p) const { return x*(ll)p.y - y*(ll)p.x; }
+	friend istream& operator >> (istream& in, pt& p) {
+		return in >> p.x >> p.y;
+	}
+};
+
+struct line { // reta
+	pt p, q;
+	line() {}
+	line(pt p_, pt q_) : p(p_), q(q_) {}
+	friend istream& operator >> (istream& in, line& r) {
+		return in >> r.p >> r.q;
+	}
+};
+
+// PONTO & VETOR
+
+ll dist2(pt p, pt q) { // quadrado da distancia
+	return sq(p.x - q.x) + sq(p.y - q.y);
+}
+
+ll sarea2(pt p, pt q, pt r) { // 2 * area com sinal
+	return (q-p)^(r-q);
+}
+
+bool col(pt p, pt q, pt r) { // se p, q e r sao colin.
+	return sarea2(p, q, r) == 0;
+}
+
+bool ccw(pt p, pt q, pt r) { // se p, q, r sao ccw
+	return sarea2(p, q, r) > 0;
+}
+
+int quad(pt p) { // quadrante de um ponto
+	return (p.x<0)^3*(p.y<0);
+}
+
+bool compare_angle(pt p, pt q) { // retorna se ang(p) < ang(q)
+	if (quad(p) != quad(q)) return quad(p) < quad(q);
+	return ccw(q, pt(0, 0), p);
+}
+
+pt rotate90(pt p) { // rotaciona 90 graus
+	return pt(-p.y, p.x);
+}
+
+int main()
+{
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    int n;
+    cin >> n;
+
+    V<pair<pt, int>> fds(n);
+    rep(i, n) {
+        cin >> fds[i].first;
+        fds[i].second = i + 1;
+    }
+
+    sort(all(fds), [&](pair<pt, int> &a, pair<pt, int> &b) {
+            return compare_angle(a.first, b.first);
+         });
+
+    auto better = [&](pt &a, pt &b, pt &c, pt &d) {
+        pt p1(a * b, abs(a ^ b));
+        pt p2(c * d, abs(c ^ d));
+        return (p1 ^ p2) > 0;
+    };
+
+    int ans1 = 0;
+    int ans2 = 1;
+    nrep(i, 1, n - 1) {
+        pt &one = fds[i].first;
+        pt &two = fds[i + 1].first;
+        if (better(one, two, fds[ans1].first, fds[ans2].first)) {
+            ans1 = i;
+            ans2 = i + 1;
+        }
+    }
+
+    pt &one = fds.back().first;
+    pt &two = fds[0].first;
+    if (better(one, two, fds[ans1].first, fds[ans2].first)) {
+        ans1 = n - 1;
+        ans2 = 0;
+    }
+
+    cout << fds[ans1].second << ' ' << fds[ans2].second << '\n';
+}