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<algorithm>
using namespace std;
int p[101],r[101];
void makeset(int x){
    for(int i=0;i<x;++i){
        p[i]=i;
        r[i]=0;
    }
}
int root(int a){
    if(a!=p[a])
        p[a]=root(p[a]);
    return p[a];
}
bool same(int a,int b){
    return (root(a)==root(b));
}
void link(int a,int b){
    if(r[a]>r[b]){
        p[b]=a;
    }
    else{
        p[a]=b;
        if(r[a]==r[b]){
            r[b]++;
        }
    }
}
void unite(int a,int b){
    link(root(a),root(b));
}
struct Edges{int cost,src,dst;}edges[10010];
bool operator<(const Edges &x,const Edges &y){return x.cost<y.cost;}
int main(){
    int N,M=0;
    int A[101][101];
    cin>>N;
    makeset(N);
    for(int r=0;r<N;++r){
        for(int c=0;c<N;++c){
            cin>>A[r][c];
        }
        for(int c=r+1;c<N;++c){
            if(A[r][c]>-1){
                edges[M].cost=A[r][c];
                edges[M].src=r;
                edges[M].dst=c;
                M+=1;
            }
        }
    }
    sort(edges,edges+M);
    int total=0,num=0,flag=0;
    for(int i=0;i<M;++i){
        if(same(edges[i].src,edges[i].dst)){continue;}
        else{
            unite(edges[i].src,edges[i].dst);
            total+=edges[i].cost;
            num++;
        }
        if(num==N-1){
            flag=1;
            break;
        }
    }
    if(flag){
        cout<<total<<endl;
    }
}

C++: #include <bits/stdc++.h>
#define MOD 1000000007
#define INF 1<<30
#define rep(i,n) for(ll i=0; i<(n); i++)
#define REP(i,a,b) for(ll i=(a); i<(b); i++)
#define RREP(i,a,b) for(ll i=(a); i>=(b); i--)
#define all(x) (x).begin(),(x).end()
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef pair<ll, ll> p;
typedef vector<pair<ll, ll>> vpl;

vvl m(105, vl(105,INF));
ll n;

ll prim(){
    ll u, minv=INF;
    vl visit(105,0);
    vl d(105,INF);
    vl p(105,-1);

    d[0] = 0;
    while(1){
        minv = INF;
        rep(i,n){
            if(d[i] < minv && visit[i] == 0){
                minv = d[i];
                u = i;
            }
        }
        if(minv == INF) break;
        visit[u] = 1;
        rep(i,n){
            if(visit[i] == 0 && m[u][i] != INF){
                if(d[i] > m[u][i]){
                    d[i] = m[u][i];
                    p[i] = u;
                }
            }
        }
    }
    ll sum=0;
    rep(i,n){
        if(p[i] != -1) sum += d[i];
    }
    return sum;
}

int main(){
    ll t;
    cin >> n;
    rep(i,n){
        rep(j,n){
            cin >> t;
            m[i][j] = (t==-1) ? INF : t;
        }
    }

    cout << prim() << "\n";

    return 0;
}

C++: #include<iostream>
#include<vector>
#include<utility>
using namespace std;
enum COLOR{WHITE, GRAY, BLACK};

int main(){
    int n;
    cin >> n;
    vector<vector<int> > G(n, vector<int>(n));
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> G[i][j];
            if (G[i][j] == -1) G[i][j] = 1e8;
        }
    }
    vector<COLOR> COL(n, WHITE);
    COL[0] = GRAY;
    int sum = 0;
    while (1) {
        pair<int, int> min_bridge = make_pair(0, 0);
        for (int i = 0; i < n; i++) {
            if (COL[i] != GRAY) continue;
            bool flag = true;
            for (int j = 0; j < n; j++) {
                if (COL[j] != WHITE) continue;
                flag = false;
                if (G[i][j] < G[min_bridge.first][min_bridge.second]) {
                    min_bridge.first  = i;
                    min_bridge.second = j;
                }
            }
            if (flag) COL[i] = BLACK;
        }
        if (min_bridge.first == 0 && min_bridge.second == 0) break;
        COL[min_bridge.second] = GRAY;
        sum += G[min_bridge.first][min_bridge.second];
    }
cout << sum << endl;
    return 0;
}