Create triangles.cpp

1 files changed, 113 insertions, 0 deletions

diff --git a/2016/December/Platinum/triangles.cpp b/2016/December/Platinum/triangles.cpp
new file mode 100644
index 0000000..1a2fdd9
--- /dev/null
+++ b/2016/December/Platinum/triangles.cpp
@@ -0,0 +1,113 @@
+#include <algorithm>
+#include <iostream>
+#include <fstream>
+#include <cstring>
+#include <vector>
+#include <cmath>
+using namespace std;
+typedef long long ll;
+typedef pair<int, int> ii;
+typedef vector<int> vi;
+typedef vector<ii> vii;
+
+struct point {
+	ll x, y;
+	point() { x = y = 0; }
+	point(ll _x, ll _y) : x(_x), y(_y) {}
+	bool operator < (point p) const {
+		return (x == p.x && y < p.y) || x < p.x;
+	}
+	bool operator == (point p) const {
+		return x == p.x && y == p.y;
+	}
+} T[305];
+
+struct vec {
+	ll x, y;
+	vec(ll _x, ll _y) : x(_x), y(_y) {}
+};
+
+vec to_vec(point a, point b) {
+	return vec(b.x - a.x, b.y - a.y);
+}
+
+ll dot(vec a, vec b) {
+	return (a.x * b.x + a.y * b.y);
+}
+
+ll norm_sq(vec v) {
+	return v.x * v.x + v.y * v.y;
+}
+
+ll cross(vec a, vec b) {
+	return a.x * b.y - a.y * b.x;
+}
+
+bool ccw(point p, point q, point r) {
+	return cross(to_vec(p, q), to_vec(p, r)) > 0;
+}
+
+struct line { ll a, b, c; };
+
+line to_line(point p1, point p2) {
+	return { p2.y - p1.y, p1.x - p2.x, p1.x * p2.y - p1.y * p2.x };
+}
+
+class fenwick_tree {
+private: vector<int> FT;
+public:
+	fenwick_tree(int N) { FT.assign(N + 1, 0); }
+	void update(int x, int val) { for (; x < FT.size(); x += x & -x) FT[x] += val; }
+	int query(int x) { int ret = 0; for (; x > 0; x -= x & -x) ret += FT[x]; return ret; }
+	int query(int x, int y) { return query(y) - (x == 1 ? 0 : query(x - 1)); }
+};
+
+int ans[305] = { 0 };
+
+int main() {
+	ifstream cin("triangles.in");
+	ofstream cout("triangles.out");
+	
+	int N;
+	cin >> N;
+	for (int i = 0; i < N; i++) cin >> T[i].x >> T[i].y;
+	sort(T, T + N);
+
+	for (int i = 0; i < N - 1; i++) {
+		for (int j = i + 1; j < N; j++) {
+			line L = to_line(T[i], T[j]);
+
+			vector<pair<ii, point>> A, B;
+			for (int k = i + 1; k < N; k++) {
+				if (k != i && k != j) {
+					if (T[k].x * L.a + T[k].y * L.b < L.c) {
+						A.emplace_back(ii(k, k), T[k]);
+					}
+				}
+			}
+
+			vector<ii> l, r;
+			int N = A.size();
+			for (int i = 0; i < N; i++) {
+				l.emplace_back(A[i].first.first, i);
+				r.emplace_back(A[i].first.second, i);
+			}
+			sort(l.begin(), l.end(), [i](const ii& a, const ii& b) { return ccw(T[b.first], T[i], T[a.first]); });
+			sort(r.begin(), r.end(), [j](const ii& a, const ii& b) { return ccw(T[a.first], T[j], T[b.first]); });
+			for (int i = 0; i < N; i++) {
+				A[l[i].second].first.first = i + 1;
+				A[r[i].second].first.second = i + 1;
+			}
+
+			sort(A.begin(), A.end());
+
+			fenwick_tree FT(N);
+			for (auto& p : A) {
+				ans[FT.query(p.first.second)]++;
+				FT.update(p.first.second, 1);
+			}
+		}
+	}
+
+	for (int i = 0; i < N - 2; i++) cout << ans[i] << endl;
+}