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;
typedef long long ll;
#define rep(i, start, n) for (int i = (int)(start); i < (int)(n); ++i)
static const int MAX = 100;
static const int INFTY = (1 << 30);
static const int WHITE = 0;
static const int GRAY = 1;
static const int BLACK = 2;
int n, M[MAX][MAX]; //nは要素数、Mは隣接行列
int prim()
{
    int u, minv;                    //uは最短距離の相手、minvは最短距離
    int d[MAX], p[MAX], color[MAX]; //dは始点からの距離、pは親,colorは訪問状態
    rep(i, 0, n)                    //初期設定
    {
        d[i] = INFTY;
        p[i] = -1;
        color[i] = WHITE; //未訪問
    }
    d[0] = 0; //始点のdは0
    while (1)
    {
        minv = INFTY;
        u = -1;
        rep(i, 0, n) //未完了の点のうち始点からの最短距離は？
        {
            if (minv > d[i] && color[i] != BLACK) //未完了の点がある
            {
                u = i;
                minv = d[i];
            }
        }
        if (u == -1)
            break;
        color[u] = BLACK;
        rep(i, 0, n)
        {
            if (color[i] != BLACK && M[u][i] != INFTY)
            {
                if (d[i] > M[u][i])
                {
                    d[i] = M[u][i];
                    p[i] = u;
                    color[i] = GRAY;
                }
            }
        }
    }
    int sum = 0;
    rep(i, 0, n)
    {
        if (p[i] != -1)
            sum += M[i][p[i]];
    }
    return sum;
}
int main()
{
    cin >> n;
    rep(i, 0, n)
    {
        rep(j, 0, n)
        {
            int e;
            cin >> e;
            M[i][j] = (e == -1) ? INFTY : e;
        }
    }
    cout << prim() << endl;
}

C++: 

#include <iostream>
using namespace std;
#define INFTY  (1 << 30)//极大值
#define NIL  -1
const int TOTAL = 101;
int totalnode,color[TOTAL], matrix[TOTAL][TOTAL], DistanceBetweenParent[TOTAL], parent[TOTAL];//颜色0白色，1为灰色，2是黑色
void includeMinimumSpanningTree()
{
	int u,min;
	DistanceBetweenParent[0] = 0;//这个点到其父节点的距离为0
	parent[0] = -1;//根的父节点为-1
	while (1)
	{
		min = INFTY;
		for (int i = 0; i < totalnode; i++)//找出非黑色同时到父节点加权值最少的节点
			if (color[i] != 2 && DistanceBetweenParent[i] < min)//第一次只有根
				min = DistanceBetweenParent[i], u = i;//以u寻找连接它的其他点
		color[u] = 2;//u的颜色为黑色
		if (min == INFTY)break;//寻找结束
		for (int i = 0; i < totalnode; i++)//寻找相连的点
		{
			if (color[i] != 2 && matrix[u][i]!= -1)//未发现且存在边
			{
				if (matrix[u][i] < DistanceBetweenParent[i])//当前点连接父节点的加权值大于新的加权值
				{
					color[i] = 1;//灰色
					DistanceBetweenParent[i] = matrix[u][i];
					parent[i] = u;
				}
			}
		}
	}
}
int main()
{	
	int inputdata,minmum=0;
	cin >> totalnode;
	for (int i = 0; i < totalnode; i++)color[i] = 0;//颜色初始化
	for(int i = 0; i < totalnode; i++)DistanceBetweenParent[i] = INFTY;//将距离初始化为最大值
	for (int i = 0; i < totalnode; i++)//顶点i 到顶点j的距离，不存在的为-1；
		for (int j = 0; j < totalnode; j++)
			cin >> inputdata, matrix[i][j] = inputdata;
	includeMinimumSpanningTree();
	for (int i = 0; i < totalnode; i++)
		minmum += DistanceBetweenParent[i];
	cout << minmum << endl;

}

C++: 
#include<stdio.h>

#define MAX 100
#define INFINITY 10000

int n;
int M[MAX][MAX], color[MAX], d[MAX], p[MAX];

enum {
    WHITE,
    GRAY,
    BLACK
};

int prim() {
    for (int i = 0; i < n; ++i) {
        color[i] = WHITE;
        d[i] = INFINITY;
        p[i] = -1;
    }
    d[0] = 0;
    p[0] = -1;

    while (true) {
        int min = INFINITY;
        int target = -1;
        for (int i = 0; i < n; ++i) {
            if (d[i] < min && color[i] != BLACK) {
                min = d[i];
                target = i;
            }
        }
        if (target == -1) break;

        color[target] = BLACK;

        for (int v = 0; v < n; ++v) {
            if (color[v] != BLACK && M[target][v] > 0) {
                if(M[target][v] < d[v]) {
                    d[v] = M[target][v];
                    p[v] = target;
                    color[v] = GRAY;
                }
            }
        }
    }

    int sum = 0;
    for (int i = 0; i < n; ++i) {
        if (p[i] != -1) sum += M[i][p[i]];
    }
    return sum;
}

int main() {
    scanf("%d", &n);
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            scanf("%d", &M[i][j]);
        }
    }
    printf("%d\n", prim());
    return 0;
}