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>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>

using namespace std;

#define MAX_N 100

int G[MAX_N][MAX_N];

int mincost[MAX_N];
bool used[MAX_N];
int V;
int prim() {
	for (int i = 0; i < V; i++) {
		mincost[i] = INT_MAX;
		used[i] = false;
	}
	mincost[0] = 0;
	int res = 0;

	while (1) {
		int v = -1;
		for (int u = 0; u < V; u++)
			if (!used[u] && (v == -1 || mincost[u] < mincost[v]) )
				v = u;

		if (v == -1)
			break;
		used[v] = true;
		res += mincost[v];

		for (int u = 0; u < V; u++)
			mincost[u] = min(mincost[u], G[v][u]);
	}
	return res;
}

int main() {
	int n, c;
	cin >> n;
	V = n;
	for (int i = 0; i < n; i++)
		for (int j = 0; j < n; j++) {
			cin >> c;
			if (c == -1) c = INT_MAX;
			G[i][j] = c;
		}

	cout << prim() << endl;
	return 0;
}

C++: #include<bits/stdc++.h>
#define REP(i,n) for(long long i=0;i<n;++i)
#define FOR(i,a,b) for(long long i=a;i<b;++i)
using namespace std;
const int MAX=100,INF=1<<30,WHI=0,GRA=1,BLA=2;
int n,m[MAX][MAX];
int prim(){
    int u,minv;
    int d[MAX],p[MAX],color[MAX];
    fill(d,d+n+1,INF);
    fill(p,p+n+1,-1);
    fill(color,color+n+1,WHI);
    d[0]=0;
    while(1){
        minv=INF;
        u=-1;
        REP(i,n){
            if(minv>d[i]&&color[i]!=BLA){
                u=i;
                minv=d[i];
            }
        }
        if(u==-1) break;
        color[u]=BLA;
        REP(v,n){
            if(color[v]!=BLA&&m[u][v]!=INF){
                if(m[u][v]<d[v]){
                    d[v]=m[u][v];
                    p[v]=u;
                    color[v]=GRA;
                }
            }
        }
    }
    int sum=0;
    REP(i,n){
        if(p[i]!=-1) sum+=m[i][p[i]];
    }
    return sum;
}
int main(){
    scanf("%d",&n);
    REP(i,n){
        REP(j,n){
            int e;
            scanf("%d",&e);
            m[i][j]=(e==-1)?INF:e;
        }
    }
    printf("%d\n",prim());
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

typedef long long ll;


class Union_Find {
private:
    std::vector<int> par;
    std::vector<int> rank;

public:
    Union_Find(int n) { // ?????????: O(n)
	par = rank = std::vector<int>(n);
	for(int i=0; i<n; i++) {
	    par[i]  = i;
	    rank[0] = 0;
	}
    }

    int root(int x) { // ??¨??????????±???????: O(?±(n)) 
	if(par[x] == x) return x;
	return par[x] = root(par[x]); // ??????????????????????????????????????????
    }

    void unite(int x, int y) { // x,y????????????????????????: O(?±(n)) 
	x = root(x); y = root(y);
	if( x == y ) return;

	if( rank[x] < rank[y] ) par[x] = y;
	else {
	    par[y] = x;
	    if( rank[x] == rank[y] ) rank[x]++;
	}
    }

    bool same(int x, int y) { //x,y??????????????????????????????????????????: O(?±(n)) 
	return root(x) == root(y);
    }
};

struct Edge {
    ll s,t;
    ll w;
    bool operator < (const Edge& tgt) const {
	return w > tgt.w;
    }
};

ll Kruskal(priority_queue<Edge>& edges, const int V) {

    ll res = 0;
    
    Union_Find uf(V);
    while( !edges.empty() ) {
	Edge e = edges.top(); edges.pop();
	if( !uf.same(e.s, e.t) ) {
	    uf.unite(e.s, e.t);
	    res += e.w;
	}
    }
    return res;
}


int main () {

    ll V;
    cin >> V;

    priority_queue<Edge> edges;
    
    for(int i=0; i<V; i++) {
	for(int j=0; j<V; j++) {
	    ll d;
	    cin >> d;
	    if( d != -1 )
		edges.push( Edge{i,j,d} );
	}	
    }

    ll res = Kruskal(edges,V);
    cout << res << endl;    
    return 0;
}