Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

const (
	MAX_N      = 200
	MAX_WEIGHT = 2000
)

type Edge struct {
	start  int
	end    int
	weight int
}

type ShortestInfo struct {
	edges    []Edge
	shortest int
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}

	shortestList := make([]ShortestInfo, n)
	for i := 1; i < n; i++ {
		shortestList[i] = ShortestInfo{edges: []Edge{}, shortest: MAX_N*MAX_WEIGHT + 1}
	}

	adjacentMatrix := make([][]int, n)
	for i := 0; i < n; i++ {
		adjacentMatrix[i] = make([]int, n)
		for j := 0; j < n; j++ {
			v, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			adjacentMatrix[i][j] = v
		}
	}

	mst([]int{1}, shortestList, adjacentMatrix)
	fmt.Println(calculateMinWeight(shortestList))
}

func calculateMinWeight(shortestList []ShortestInfo) int {
	visitedList := make([]bool, len(shortestList))
	visitedList[0] = true
	sumWeight := 0
	for !visitedAll(visitedList) {
		shortestInfo := shortestList[0]
		shortestList = shortestList[1:]
		edges := shortestInfo.edges
		for _, edge := range edges {
			if !visitedList[edge.end-1] {
				visitedList[edge.end-1] = true
				sumWeight += edge.weight
			}
		}
	}
	return sumWeight
}

func visitedAll(visitedList []bool) bool {
	for _, v := range visitedList {
		if !v {
			return false
		}
	}
	return true
}

func mst(nodeStack []int, shortestList []ShortestInfo, adjacentMatrix [][]int) {
	for len(nodeStack) > 0 {
		currentNode := nodeStack[0]
		nodeStack = nodeStack[1:]
		currentShortest := getShortest(currentNode, shortestList)
		adjacents := findAdjacents(currentNode, adjacentMatrix)
		for i := 0; i < len(adjacents); i++ {
			adj := adjacents[i]
			s := getShortest(adj.end, shortestList)
			if currentShortest.shortest+adj.weight < s.shortest || (currentShortest.shortest+adj.weight == s.shortest && len(currentShortest.edges)+1 > len(s.edges)) {
				setShortest(adj.end, adj, currentShortest, shortestList)
				nodeStack = append(nodeStack, adj.end)
			}
		}
	}
}

func getShortest(node int, shortestList []ShortestInfo) ShortestInfo {
	return shortestList[node-1]
}

func setShortest(node int, edge Edge, currentShortest ShortestInfo, shortestList []ShortestInfo) {
	newEdges := make([]Edge, len(currentShortest.edges)+1)
	for i := 0; i < len(newEdges)-1; i++ {
		newEdges[i] = currentShortest.edges[i]
	}
	newEdges[len(newEdges)-1] = edge
	shortestInfo := ShortestInfo{edges: newEdges, shortest: currentShortest.shortest + edge.weight}
	shortestList[node-1] = shortestInfo
}

func findAdjacents(currentNode int, adjacentMatrix [][]int) []Edge {
	adjacents := adjacentMatrix[currentNode-1]
	edges := []Edge{}
	for i, v := range adjacents {
		if v > 0 {
			edges = append(edges, Edge{start: currentNode, end: i + 1, weight: v})
		}
	}
	return edges
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

C++: #include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <deque>
#include <bitset>
#include <numeric>
#include <sstream>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <stack>
#include <tuple>

using namespace std;

#define int long long

#define rep(i,n) for(int i = 0; i<n ; i++)
#define FOR(i,a,n) for(int i=a; i<n; i++)
#define REPSTR(i,s) for(int i=0; (s)[i]; i++)
#define REPITR(i,s) for(auto i=(s).begin(); i!=(s).end();i++)

#define RANGE(a,i,b) ((a)<=(i)&&(i)<=(b))

#define pb push_back
#define mp make_pair

#define ALL(a) begin(a), end(a)

#define EXIST(s,x) ((s).find(x)!=(s).end())

#define SET(a,c) memset(a,c,sizeof(a))
#define CLR(a) memset(a,0,sizeof(a))

#ifdef _DEBUG
#define DEBUG(x) cerr<<#x<<":"<<x<<endl
#else
#define DEBUG(x)
#endif

#define PRINTJOIN(x,n) rep(i,n){if(i)cout<<" ";cout<<x[i];}cout<<endl 

#define INF 1001001001
#define LLINF 1001001001001001001LL

typedef long long ll;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef stringstream SS;

#define PQ priority_queue

#define FST first
#define SEC second

int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };

template<typename T>
class UnionFind {
    public:
    vector<T> parent;
    vector<T> rank;
    UnionFind() {}
    UnionFind(T n):parent(n), rank(n){
        rep(i, n) {
            parent[i]=i;
        }
        fill(ALL(rank), 0);
    }
    T root(T x) {
        if(parent[x] == x){
            return x;
        } else {
            parent[x] = root(parent[x]);
            return parent[x];
        }
    }
    bool same(T x, T y) {
        return root(x) == root(y);
    }
    void unite(T x, T y) {
        x = root(x);
        y = root(y);
        if (x == y) return;
        if (rank[x] < rank[y]) {
            parent[x] = y;
        } else {
            parent[y] = x;
            if(rank[x] == rank[y]) rank[x]++;
        }
    }
};

signed main(void) {
	cin.tie(0);
	ios::sync_with_stdio(false);
    int n;
    cin>>n;
    priority_queue<tuple<int,int,int>, vector<tuple<int,int,int>>, greater<tuple<int,int,int>>> q;
    rep(i,n)rep(j,n){
        int t;cin>>t;
        if(t != -1) {
            q.push(make_tuple(t, i, j));
        }
    }
    UnionFind<int> uf(n);
    int ans = 0;
    while(!q.empty()) {
        tuple<int,int,int> t = q.top();q.pop();
        int c,x,y;
        c=get<0>(t);
        x=get<1>(t);
        y=get<2>(t);
        if(!uf.same(x,y)) {
            ans += c;
            uf.unite(x,y);
        }
    }
    cout<<ans<<endl;
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <list>

#define INFTY 1000000001

class Graph{
public:
	std::vector< std::vector<int> > A;
	int n;

	Graph(int n);

	void SetEdge(int a, int b, int weight);
	void SortEdge();
	void SortEdge_Rec1(int left, int right);
	void SortEdge_Rec2(int left, int mid, int right);

	int Kruskal();

};

Graph::Graph(int n){;
	this->n = n;
}

void Graph::SetEdge(int a, int b, int weight){
	std::vector<int> x;
	x.push_back(a); x.push_back(b); x.push_back(weight);
	A.push_back(x);
	return;
}

void Graph::SortEdge(){
	SortEdge_Rec1(0, A.size());
}

void Graph::SortEdge_Rec1(int left, int right){
	if (left + 1 < right){
		int mid = (left + right) / 2;
		SortEdge_Rec1(left, mid);
		SortEdge_Rec1(mid, right);
		SortEdge_Rec2(left, mid, right);
	}
}

void Graph::SortEdge_Rec2(int left, int mid, int right){
	int n1 = mid - left;
	int n2 = right - mid;
	std::vector< std::vector<int> > L(n1 + 1);
	for (int i = 0; i < n1; i++) L[i] = A[left + i];
	std::vector< std::vector<int> > R(n2 + 1);
	for (int i = 0; i < n2; i++) R[i] = A[mid + i];
	std::vector<int> x;
	x.push_back(0); x.push_back(0); x.push_back(INFTY);
	L[n1] = x;
	R[n2] = x;
	int i = 0;
	int j = 0;
	for (int k = left; k < right; k++){
		if (L[i][2] <= R[j][2]){
			A[k] = L[i];
			i = i + 1;
		}
		else{
			A[k] = R[j];
			j = j + 1;
		}
	}
}

int Graph::Kruskal(){
	std::vector<int> f(n);
	for (int i = 0; i < n; i++) f[i] = i;
	int branch = 0;

	while (!A.empty()){
		std::vector<int> e = A[0];
		A.erase(A.begin());
		if (f[e[0]] != f[e[1]]){
			int tmp = f[e[1]];
			for (int i = 0; i < n; i++) if (f[i] == tmp) f[i] = f[e[0]];
			branch += e[2];
		}
	}
	return branch;
}

int main(){
	int n, e;
	scanf("%d", &n);
	Graph G(n);
	for (int i = 0; i < n; i++){
		for (int j = 0; j < n; j++){
			scanf("%d", &e);
			if (j >= i && e != -1) G.SetEdge(i, j, e);
		}
	}

	G.SortEdge();

	printf("%d\n", G.Kruskal());

	return 0;
}