Go: package main

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

// Define disjoint-set forests

type vertexNo int

type vertex struct {
	number vertexNo
	rank int
	parent *vertex
}

func makeSet(number vertexNo) vertex {
	return vertex {
		number: number,
		rank: 0,
		parent: nil,
	}
}

func union(x, y *vertex) *vertex {
	return link(findSet(x), findSet(y))
}

func link(x, y *vertex) *vertex {
	if x.rank > y.rank {
		y.parent = x
		return x
	} else {
		x.parent = y
		if x.rank == y.rank {
			y.rank += 1
		}
		return y
	}
}

func findSet(v *vertex) *vertex {
	if v.parent == nil {
		return v
	}
	v.parent = findSet(v.parent)
	return v.parent
}

// Function to calculate minimum spanning tree

type matrix [][]int

type edge struct {
	one vertexNo
	two vertexNo
	weight int
}

const(
	MAX_VERTICES = 100
)

func newEdgesFromMatrix(matrix matrix) []edge {
	edges := make([]edge, 0, MAX_VERTICES * MAX_VERTICES)

	for i := 0; i < len(matrix); i++ {
		row := matrix[i]
		for j := i; j < len(row); j++ {
			if row[j] >= 0 {
				edge := edge{one: vertexNo(i+1), two: vertexNo(j+1), weight: row[j]}
				edges = append(edges, edge)
			}
		}
	}

	return edges
}

func solve(matrix matrix) int {
	nVertices := len(matrix)

	// initialize vertices
	vertices := make([]vertex, nVertices)
	for i := 0; i < nVertices; i++ {
		vertices[i] = makeSet(vertexNo(i+1))
	}

	// prepare edges sorted in the ascending order of weight
	edges := newEdgesFromMatrix(matrix)
	sort.Slice(edges, func(i, j int) bool {
		return edges[i].weight < edges[j].weight
	})

	unionCount := 0
	weightSum := 0
	for unionCount < nVertices-1 {
		for i := 0; i < len(edges); i++ {
			edge := edges[i]
			v1 := &vertices[edge.one-1]
			v2 := &vertices[edge.two-1]
			rep1 := findSet(v1)
			rep2 := findSet(v2)
			if rep1.number == rep2.number {
				continue
			}
			union(rep1, rep2)
			edges = append(edges[0:i], edges[i+1:]...)
			weightSum += edge.weight
			unionCount++
			break
		}
	}

	return weightSum
}

// main

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

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

	matrix := parseMatrix(n, sc)

	edges := newEdgesFromMatrix(matrix)
	sort.Slice(edges, func(i, j int) bool {
		return edges[i].weight < edges[j].weight
	})

	fmt.Println(solve(matrix))
}

func parseMatrix(n int, sc *bufio.Scanner) [][]int {
	matrix := make([][]int, n)
	for i := 0; i < n; i++ {
		matrix[i] = make([]int, n)
		for j := 0; j < n; j++ {
			x, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			matrix[i][j] = x
		}
	}
	return matrix
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

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

Python: n = int(raw_input())
a = []

for i in range(n):
    inp = raw_input()
    if "-1" in inp:
        inp = inp.replace("-1","10000")
    a.append(list(map(int, inp.split())))

w = 0
v = set()
v.add(0)

while len(v) < n:
    min_w   = 10000
    min_idx = 0
    i = 0
    for node in v:
        if min_w > min(a[node]):
            min_w = min(a[node])
            i = node
            min_idx = a[i].index(min_w)
    if min_idx in v:
        a[i][min_idx] = 10000
        continue
    else:
        w += min_w
        v.add(min_idx)

print(w)

Python: n=int(input())
M=[list(map(int,input().split()))for _ in[0]*n]
d=[0]+[1e4]*n
b=[1]*n
a=0
while 1:
 u=-1
 for i in range(n):
  if b[i]and(u<0 or d[i]<d[u]):u=i
 if u<0:break
 b[u]=0
 a+=d[u]
 for v in range(n):
  t=M[u][v]
  if t+1 and d[v]>t:d[v]=t
print(a)

Python: def prim(n,M):
    d = [None]*n
    p = [None]*n
    searched = [0]*n
    
    for i in range(n):
        d[i] = float("inf")
        p[i] = -1
    
    d[0] = 0
    
    while True:
        minv = float("inf")
        u = -1
        for i in range(n):
            if minv > d[i] and not searched[i]:
                u = i
                minv = d[i]
        
        if u == -1:
            break
        searched[u] = 1
        for v in range(n):
            if (not searched[v]) and M[u][v] != -1:
                if d[v] > M[u][v]:
                    d[v] = M[u][v]
                    p[v] = u

    s = 0
    for i in range(n):
        if p[i] != -1:
            s += M[i][p[i]]
    return print(s)

n = int(input())
M = [list(map(int,input().split())) for _ in range(n)]
prim(n,M)

Python: #!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys

WHITE, GRAY, BLACK = 0, 1, 2


def prim_span_tree():
    min_weight_vertices[0] = 0

    while True:
        min_cost = 2001
        current_vertex = -1
        for i in range(vertices_num):
            if color[i] != BLACK and min_weight_vertices[i] < min_cost:
                min_cost = min_weight_vertices[i]
                current_vertex = i

        if min_cost == 2001:
            break

        color[current_vertex] = BLACK

        for j in range(vertices_num):
            v_weight = int(init_vertices_matrix[current_vertex][j])
            if color[j] != BLACK and v_weight >= 0:
                if v_weight < min_weight_vertices[j]:
                    min_weight_vertices[j] = v_weight
                    parent_list[j] = current_vertex
                    color[j] = GRAY

    return min_weight_vertices


if __name__ == '__main__':
    _input = sys.stdin.readlines()
    vertices_num = int(_input[0])
    init_vertices_matrix = list(map(lambda x: x.split(), _input[1:]))

    parent_list, min_weight_vertices = [-1] * vertices_num, [2001] * vertices_num
    color = [WHITE] * vertices_num
    ans = prim_span_tree()
    print(sum(ans))

Python: 
def prim(cost):
    sumcost = 0
    V = len(cost)
    mincost = [float('inf')] * V
    used = [False] * V
    mincost[0] = 0
    while True:
        j = -1
        for i in range(V):
            if not used[i] and (j == -1 or mincost[i] < mincost[j]):
                j = i
        if j == -1:
            break
        used[j] = True
        sumcost = sumcost + mincost[j]
        for i in range(V):
            if cost[i][j] == -1:
                continue
            mincost[i] = min(mincost[i], cost[j][i])
    return sumcost

n = int(raw_input())
A = [0] * n
for i in range(n):
    A[i] = map(int, raw_input().split())

result = prim(A)
print(result)

Python: INFTY = 1 << 21
WHITE = 0
GRAY = 1
BLACK = 2
d = [INFTY for i in range(n)]
p = [-1 for i in range(n)]
color = [WHITE for i in range(n)]

n = int(input())
M = [list(map(int, input().split())) for i in range(n)]
for i in range(n):
    for j in range(n):
        if (M[i][j] == -1):
            M[i][j] = INFTY

def prim():
    global M, d, p, color
    d[0] = 0
    while(1):
        minv = INFTY
        u = -1
        for i in range(n):
            if (minv > d[i] and color[i] != BLACK):
                u = i
                minv = d[i]
        if (u == -1):
            break
        color[u] = BLACK
        for v in range(n):
            if (color[v] != BLACK and M[u][v] != INFTY):
                if (d[v] > M[u][v]):
                    d[v] = M[u][v]
                    p[v] = u
                    color[v] = GRAY
    
    return sum([M[i][p[i]] for i in range(n) if (p[i] != -1)])

print(prim())

Python: def root(x):
    path = []
    while P[x] != x:
        path.append(x)
        x = P[x]
    for node in path:
        P[node] = x
    return x
def check(x,y):
    if root(x) == root(y):
        return 1
    else:
        return 0
def unite(x,y):
    P[root(x)] = root(y)        

n = int(input())
P = [i for i in range(n)]
omomi = []
for k in range(n):
    s = list(map(int,input().split()))
    for l in range(n):
        if s[l] != -1:
            omomi.append([s[l],k,l])
omomi.sort()
ans = 0
for yee in range(len(omomi)):
    if check(omomi[yee][1],omomi[yee][2]) == False:
            unite(omomi[yee][1],omomi[yee][2])
            ans+=omomi[yee][0]
print(ans)