Language: C++

#include "bits/stdc++.h"
#include<unordered_map>
#include<unordered_set>
#pragma warning(disable:4996)
using namespace std;
using ld = double;
const ld eps = 1e-9;

// < "d:\d_download\visual studio 2015\projects\programing_contest_c++\debug\a.txt" > "d:\d_download\visual studio 2015\projects\programing_contest_c++\debug\b.txt"
typedef ld Weight;

const Weight INF = 1e18;
const Weight ZERO = 0;
struct Edge {
	int src, dst;
	Weight weight;
	int id;
	Edge(int src_, int dst_, Weight weight_, const int id_) :
		src(src_), dst(dst_), weight(weight_), id(id_) { }
	Edge(int src, int dst, Weight weight) :
		src(src), dst(dst), weight(weight) { }
	Edge() :src(0), dst(0), weight(0) {
	}
};
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;
namespace getcycle {
	vector<Edge>get_cycle(const Graph&g, const int start) {
		vector<Edge>prev_es(g.size());
		for (auto es : g) {
			for (auto e : es) {
				prev_es[e.dst] = e;
			}
		}
		for (int i = 0; i < int(g.size()); ++i) {
			if (i == start)continue;
			int now = i;
			vector<Edge>cycles;
			vector<int>comes(g.size(), -1);
			comes[now] = 0;
			int num = 1;
			while (1) {
				cycles.emplace_back(prev_es[now]);
				now = prev_es[now].src;
				if (comes[now] != -1) {
					cycles = vector < Edge>(cycles.begin() + comes[now], cycles.end());
					reverse(cycles.begin(), cycles.end());
					return cycles;
				}
				else if (now == start) {
					break;
				}
				comes[now] = num++;
			}
		}
		return vector<Edge>(0);
	}
}

//aoj2309テ」ツつ致arifyテ」ツ?療」ツ?淌」ツ?古」ツ??ヲツュツ」テ」ツ?療」ツ?湘・ツセツゥテ・ツ?ε」ツ?ァテ」ツ?催」ツ?ヲテ」ツ??」ツつ凝」ツ?凝」ツ?ッテ、ツクツ催ヲツ伉?
pair<Weight, Graph> chu_liu(const Graph&g, const int start, const int e_size) {

	vector<Edge>cycle_edges;
	Weight total_len = 0;
	{
		Graph tree(g.size());
		{
			Graph revg(g.size());


			for (auto es : g) {
				for (auto e : es) {
					revg[e.dst].emplace_back(e.dst, e.src, e.weight, e.id);
				}
			}
			for (int node = 0; node < int(g.size()); ++node) {
				if (node == start)continue;
				else {
					Weight amin = INF;
					Edge min_edge;
					for (auto reve : revg[node]) {
						if (amin > reve.weight) {
							amin = reve.weight;
							min_edge = Edge(reve.dst, reve.src, reve.weight, reve.id);
						}
					}
					if (amin < INF) {
						total_len += min_edge.weight;
						tree[min_edge.src].emplace_back(min_edge);
					}
				}
			}
		}
		cycle_edges = getcycle::get_cycle(tree, start);
		if (cycle_edges.empty()) {
			return make_pair(total_len, tree);
		}
	}
	vector<bool>node_is_cycle(g.size());

	/*ティツヲツ?ァツエツ?ヲツ閉ーテ」ツ?ッEdgeテ」ツ?ョテヲツ閉ーテ」ツ??」ツ?妥」ツ?ァティツ可ッテ」ツ??/
	vector<int>edge_is_cycle(e_size);

	vector<Weight>prev_lens(g.size(), ZERO);

	for (auto ce : cycle_edges) {
		node_is_cycle[ce.src] = true;
		prev_lens[ce.dst] = ce.weight;
	}
	Graph newg(g.size());
	const int compress = cycle_edges[0].src;
	/*ティツヲツ?ァツエツ?ヲツ閉ーテ」ツ?ッEdgeテ」ツ?ョテヲツ閉ーテ」ツ??」ツ?妥」ツ?ァティツ可ッテ」ツ??/
	vector<Edge>memo(e_size);
	for (int s = 0; s < int(g.size()); ++s) {
		bool src_is_cycle = node_is_cycle[s];
		for (auto e : g[s]) {
			memo[e.id] = e;
			bool dst_is_cycle = node_is_cycle[e.dst];
			if (src_is_cycle&&dst_is_cycle) {
				continue;
			}
			else if (src_is_cycle) {
				e.src = compress;
			}
			else if (dst_is_cycle) {
				e.weight -= prev_lens[e.dst];
				e.dst = compress;
			}
			newg[e.src].push_back(e);
		}
	}
	auto p = chu_liu(newg, start, e_size);
	Graph compress_tree(p.second);
	Graph ans_tree(g.size());
	for (auto es : compress_tree) {
		for (auto e : es) {
			const Edge prev_edge(memo[e.id]);
			if (node_is_cycle[prev_edge.dst]) {
				for (auto cycle_edge : cycle_edges) {
					if (cycle_edge.dst != prev_edge.dst) {
						ans_tree[cycle_edge.src].emplace_back(cycle_edge);
					}
				}
			}
			ans_tree[prev_edge.src].emplace_back(prev_edge);
		}
	}
	Weight cycle_len = 0;
	for (auto e : cycle_edges) {
		cycle_len += e.weight;
	}
	return make_pair(p.first + cycle_len, ans_tree);
}

ld getlen(const vector<ld>&a, const vector<ld>&b,const ld n) {

	ld sum = 0;
	for (int k = 0; k < a.size(); ++k) {
		sum += pow(a[k]*n - b[k], 2);
	}
	return sum;
}

ld getdis(const vector<ld>&a, const vector<ld>&b) {
	ld amin = -1e8;
	ld amax = 1e8;
	int num = 100;
	while (num--) {
		ld amid1 = (amin * 2 + amax) / 3;
		ld amid2 = (amin + amax * 2) / 3;
		ld ans1 = getlen(a, b, amid1);
		ld ans2 = getlen(a, b, amid2);
		if (ans1 < ans2) {
			amax = amid2;
		}
		else {
			amin = amid1;
		}
	}
	return getlen(a, b, amin);
}

int main() {
	int N, M; cin >> N >> M;
	vector<vector<ld>>vecs(M);
	for (int i = 0; i < M; ++i) {
		for (int j = 0; j < N; ++j) {
			ld v; cin >> v;
			vecs[i].emplace_back(v);
		}
	}
	Graph g(M);
	int aid = 0;
	for (int i = 0; i < M; ++i) {
		for (int j = 0; j < M; ++j) {
			if (i == j)continue;
			else {
				ld len = getdis(vecs[i], vecs[j]);
				g[i].push_back(Edge(i, j, len,aid++));
			}
		}
	}
	ld ans = 1e18;
	for (int i = 0; i < M; ++i) {
		vector<ld>v(N);
		auto p = chu_liu(g, i, M*(M - 1));
		ld plus = getlen(v, vecs[i],0);
		ans = min(ans, p.first+plus);
	}
	cout <<setprecision(12)<<fixed<< ans << endl;
	return 0;
}

Compiler output:
a.cc:101:109: warning: trigraph ??/ ignored, use -trigraphs to enable [-Wtrigraphs]
  101 |         /*ティツヲツ?ァツエツ?ヲツ閉ーテ」ツ?ッEdgeテ」ツ?ョテヲツ閉ーテ」ツ??」ツ?妥」ツ?ァティツ可ッテ」ツ??/
a.cc:112:109: warning: trigraph ??/ ignored, use -trigraphs to enable [-Wtrigraphs]
  112 |         /*ティツヲツ?ァツエツ?ヲツ閉ーテ」ツ?ッEdgeテ」ツ?ョテヲツ閉ーテ」ツ??」ツ?妥」ツ?ァティツ可ッテ」ツ??/
a.cc:101:9: error: unterminated comment
  101 |         /*ティツヲツ?ァツエツ?ヲツ閉ーテ」ツ?ッEdgeテ」ツ?ョテヲツ閉ーテ」ツ??」ツ?妥」ツ?ァティツ可ッテ」ツ??/
      |         ^
a.cc: In function 'std::pair<double, std::vector<std::vector<Edge> > > chu_liu(const Graph&, int, int)':
a.cc:99:45: error: expected '}' at end of input
   99 |         vector<bool>node_is_cycle(g.size());
      |                                             ^
a.cc:61:79: note: to match this '{'
   61 | pair<Weight, Graph> chu_liu(const Graph&g, const int start, const int e_size) {
      |                                                                               ^
a.cc:99:45: warning: control reaches end of non-void function [-Wreturn-type]
   99 |         vector<bool>node_is_cycle(g.size());
      |                                             ^