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<bits/stdc++.h>
using namespace std;
int n,a[101][101],f[101],k,edge,sum;
struct pp{
	int x;
	int y;
	int v;
}b[10001];
int getf(int u){
	if(u==f[u])return u;
	else return f[u]=getf(f[u]); 
}
int merge(int u,int v){
	int t1=getf(u);
	int t2=getf(v);
	if(t1!=t2){
		f[t2]=t1;
	} 
}
bool cmp(pp a,pp b){
	return a.v<b.v;
}
int main(){
	scanf("%d",&n);
	for(int i=0;i<n;i++)f[i]=i;
	for(int i=0;i<n;i++){
		for(int j=0;j<n;j++){
			scanf("%d",&a[i][j]);
			if(a[i][j]!=-1){
				b[k].v=a[i][j];
				b[k].x=i;b[k].y=j;
				k++;
			}
		}
	} 
	sort(b,b+k,cmp); 
//	for(int i=0;i<k;i++){
//		printf("%d %d %d\n",b[i].x,b[i].y,b[i].v);
//	}

	for(int i=0;i<k;i++){
		if(edge==n-1)break;
		if(getf(b[i].x)!=getf(b[i].y)){
			merge(b[i].x,b[i].y);
			sum+=b[i].v;edge++;
		}
	}
	printf("%d\n",sum);
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll INF = 1e16;
const ll mod = 1000000007;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
template<class T> inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template<class T> inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
int ctoi(char c) {
  if (c >= '0' && c <= '9') {
    return c - '0';
  }
  return 0;
}
ll factorial(ll n) {
  if (n == 1) {
    return 1;
  }
  ll ans = factorial(n-1);
  return ans*n;
}
ll gcd(ll a, ll b) {
  if (a < b) {
    ll tmp = a;
    a = b;
    b = tmp;
  }
  ll r = a%b;
  while(r != 0) {
    a = b;
    b = r;
    r = a%b;
  }
  return b;
}
ll lcm(ll a, ll b) {
  return (a/gcd(a, b))*b;
}
bool prime(ll n) {
  if (n == 1) {
    return false;
  } else {
    for (ll i = 2; i <= (ll)pow(n, 0.5); i++) {
      if (n%i == 0) return false;
    }
  }
  return true;
}
ll RepeatSquaring(ll n, ll p, ll m) {
  if (p == 0) return 1;
  if (p%2 == 0) {
    ll t = RepeatSquaring(n, p/2, m);
    return (t*t)%m;
  }
  return (n*RepeatSquaring(n, p-1, m))%m;
}

vector <ll> color(100, 0);
vector <vector <ll>> m(100, vector <ll> (100, INF));
vector <ll> d(100, INF);
vector <ll> p(100, -1);

ll prim(ll n) {
  d.at(0) = 0;
  while (true) {
    ll mincost = INF;
    ll u;
    rep(i, n) {
      if (color.at(i) != 2 && d.at(i) < mincost) {
        mincost = d.at(i);
        u = i;
      }
    }
    if (mincost == INF) {
      break;
    }
    color.at(u) = 2;
    rep(i, n) {
      if (color.at(i) != 2 && m.at(u).at(i) != INF) {
        if (m.at(u).at(i) < d.at(i)) {
          d.at(i) = m.at(u).at(i);
          p.at(i) = u;
          color.at(i) = 1;
        }
      }
    }
  }
  ll sum = 0;
  rep(i, n) {
    if (p.at(i) != -1) sum += m.at(p.at(i)).at(i);
  }
  return sum;
}

int main() {
  ll n;
  cin >> n;
  rep(i, n) {
    rep(j, n) {
      ll a;
      cin >> a;
      if (a != -1) {
        m.at(i).at(j) = a;
      }
    }
  }
  cout << prim(n) << endl;
}

C++: n = int( raw_input() )
A = [0]
p = range(1, n)
a = [ [ 0 for i in xrange(n) ] for j in xrange(n) ]
for i in xrange(n):
    a[i] = map( int,raw_input().split() )
l = 0
while p != []:
    a_min = 2001
    for i in A:
        for j in p:
            if 0 <= a[i][j] < a_min:
                a_min = a[i][j]
                add_A = j
    A.append( add_A )
    NY.remove( add_A )
    l += a_min
print l

C++: #include<iomanip>
#include<limits>
#include<thread>
#include<utility>
#include<iostream>
#include<string>
#include<algorithm>
#include<set>
#include<map>
#include<vector>
#include<stack>
#include<queue>
#include<cmath>
#include<numeric>
#include<cassert>
#include<random>
#include<chrono>
using namespace std;
typedef unsigned long long int ull;
typedef long long int ll;
typedef pair<ll,ll> pll;
typedef pair<int,int> pi;
typedef pair<double,double> pd;
typedef pair<double,ll> pdl;
#define F first
#define S second
#define MK make_pair
const ll E=1e18+7;
const ll MOD=1000000007;

vector<ll> uft;

ll search(ll where){
    if(uft[where]==where){return where;}
    else{return uft[where]=search(uft[where]);}
}

void add(ll a,ll b){
    uft[search(a)]=search(b);
}


int main(){
    ll n;
    cin>>n;
    priority_queue<vector<ll>,vector<vector<ll>>,greater<vector<ll>>> E;
    for(int i=0;i<n;i++){
        for(int t=0;t<n;t++){
            ll a;
            cin>>a;
            if(a!=-1){
                E.push({a,i,t});
            }
        }
    }
    uft.resize(n);
    for(int i=0;i<n;i++){
        uft[i]=i;
    }
    ll cost=0;
    while(!E.empty()){
        vector<ll> e=E.top();
        E.pop();
        if(search(e[1])!=search(e[2])){
            cost+=e[0];
            add(e[1],e[2]);
        }
    }
    cout<<cost<<endl;
    
    
    return 0;
}