CLOPPAIR - Closest Point Pair

problem link: CLOPPAIR

Topic: Closest Point Pair

Implementation:

	#include <bits/stdc++.h>
	using namespace std;
	#define INF 1<<30
	#define endl '\n'
	#define maxn 100005
	#define tc printf("Case %d: ", cs)
	#define tcn printf("Case %d:\n", cs);
	#define FASTIO ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	typedef long long ll;
	const double PI = acos(-1.0);
	#define dbg1(x) cerr << #x << " = " << x << endl;
	#define dbg2(x, y) cerr << #x << " = " << x << ", " << #y << " = " << y << endl;
	#define dbg3(x, y, z) cerr << #x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl;
	#define dbg4(w,x, y, z) cerr << #w << " = " << w << ", " <<#x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl;
	template < typename F, typename S >
	ostream& operator << ( ostream& os, const pair< F, S > & p ) {
	return os << "(" << p.first << ", " << p.second << ")";
	}
	template < typename T >
	ostream &operator << ( ostream & os, const vector< T > &v ) {
	os << "{";
	for (auto it = v.begin(); it != v.end(); ++it) {
	if ( it != v.begin() ) os << ", ";
	os << *it;
	}
	return os << "}";
	}
	template < typename T >
	ostream &operator << ( ostream & os, const set< T > &v ) {
	os << "[";
	for (auto it = v.begin(); it != v.end(); ++it) {
	if ( it != v.begin()) os << ", ";
	os << *it;
	}
	return os << "]";
	}
	template < typename F, typename S >
	ostream &operator << ( ostream & os, const map< F, S > &v ) {
	os << "[";
	for (auto it = v.begin(); it != v.end(); ++it) {
	if ( it != v.begin() ) os << ", ";
	os << it -> first << " = " << it -> second ;
	}
	return os << "]";
	}
	#define dbg(args...) do {cerr << #args << " : "; faltu(args); } while(0)
	clock_t tStart = clock();
	#define timeStamp dbg("Execution Time: ", (double)(clock() - tStart)/CLOCKS_PER_SEC)
	void faltu () { cerr << endl; }
	template <typename T>
	void faltu( T a[], int n ) {
	for (int i = 0; i < n; ++i) cerr << a[i] << ' ';
	cerr << endl;
	}
	template <typename T, typename ... hello>
	void faltu( T arg, const hello &... rest) { cerr << arg << ' '; faltu(rest...); }
	// Program showing a policy-based data structure.
	#include <ext/pb_ds/assoc_container.hpp> // Common file
	#include <ext/pb_ds/tree_policy.hpp>
	#include <functional> // for less
	#include <iostream>
	using namespace __gnu_pbds;
	using namespace std;
	// GNU link : https://goo.gl/WVDL6g
	typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
	tree_order_statistics_node_update>
	new_data_set;
	/**___________________________________________________**/
	struct pt {
	int x, y, id;
	};
	struct cmp_x {
	bool operator()(const pt & a, const pt & b) const {
	return a.x < b.x || (a.x == b.x && a.y < b.y);
	}
	};
	struct cmp_y {
	bool operator()(const pt & a, const pt & b) const {
	return a.y < b.y;
	}
	};
	int n;
	vector<pt> a;
	double mindist;
	pair<int, int> best_pair;
	void upd_ans(const pt & a, const pt & b) {
	double dist = sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
	if (dist < mindist) {
	mindist = dist;
	best_pair = {a.id, b.id};
	}
	}
	vector<pt> t;
	void rec(int l, int r) {
	if (r - l <= 3) {
	for (int i = l; i < r; ++i) {
	for (int j = i + 1; j < r; ++j) {
	upd_ans(a[i], a[j]);
	}
	}
	sort(a.begin() + l, a.begin() + r, cmp_y());
	return;
	}
	int m = (l + r) >> 1;
	int midx = a[m].x;
	rec(l, m);
	rec(m, r);
	merge(a.begin() + l, a.begin() + m, a.begin() + m, a.begin() + r, t.begin(), cmp_y());
	copy(t.begin(), t.begin() + r - l, a.begin() + l);
	int tsz = 0;
	for (int i = l; i < r; ++i) {
	if (abs(a[i].x - midx) < mindist) {
	for (int j = tsz - 1; j >= 0 && a[i].y - t[j].y < mindist; --j)
	upd_ans(a[i], t[j]);
	t[tsz++] = a[i];
	}
	}
	}
	int main()
	{
	FASTIO
	///*
	#ifndef ONLINE_JUDGE
	freopen("in.txt", "r", stdin);
	freopen("out.txt", "w", stdout);
	freopen("error.txt", "w", stderr);
	#endif
	//*/
	cin >> n;
	//dbg(n);
	t.resize(n);
	for (int i = 0; i < n; i++) {
	int x, y;
	cin >> x >> y;
	// dbg(x, y);
	a.push_back({x, y, i});
	//dbg(a[i].x, a[i].y, a[i].id);
	}
	sort(a.begin(), a.end(), cmp_x());
	mindist = 1e18;
	rec(0, n);
	int x = best_pair.first;
	int y = best_pair.second;
	if (x > y)swap(x, y);
	cout << x << " " << y << " " << fixed << setprecision(6) << mindist << endl;
	return 0;
	}

view raw CLOPPAIR.cpp hosted with ❤ by GitHub

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