Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() int {
	n, err := strconv.Atoi(nextString())
	if err != nil {
		fmt.Printf("strconv.Atoi failed: %v\n", err)
	}
	return n
}

type ElementKey int
type Node struct {
	key    ElementKey
	parent *Node
	rank   int
}

func newNode(key ElementKey) *Node {
	node := Node{}
	node.key = key
	node.parent = &node
	node.rank = 0

	return &node
}

func union(x, y *Node) {
	xSet := findSet(x)
	ySet := findSet(y)
	link(xSet, ySet)
}

func link(x, y *Node) {
	if x.rank > y.rank {
		y.parent = x
	} else {
		x.parent = y

		if x.rank == y.rank {
			y.rank++
		}
	}
}

func findSet(x *Node) *Node {
	if x != x.parent {
		x.parent = findSet(x.parent)
	}
	return x.parent
}

func newDisjointSets(nSets int) *DisjointSets {
	sets := DisjointSets{}
	sets.keyToNode = map[ElementKey]*Node{}
	for i := 0; i < nSets; i++ {
		key := ElementKey(i)
		sets.keyToNode[key] = newNode(key)
	}
	return &sets
}

type DisjointSets struct {
	keyToNode map[ElementKey]*Node
}

func (sets *DisjointSets) union(x, y ElementKey) {
	xNode := sets.keyToNode[x]
	yNode := sets.keyToNode[y]
	union(xNode, yNode)
}

func (sets DisjointSets) findSet(x ElementKey) *Node {
	xNode := sets.keyToNode[x]
	return findSet(xNode)
}

type Edge struct {
	i, j   int
	weight int
}

func main() {
	scanner.Split(bufio.ScanWords)

	n := nextInt()
	sets := newDisjointSets(n)
	edges := []Edge{}
	a := make([][]int, n)
	for i := 0; i < n; i++ {
		a[i] = make([]int, n)
		for j := 0; j < n; j++ {
			a[i][j] = nextInt()
			if a[i][j] >= 0 {
				e := Edge{
					i:      i,
					j:      j,
					weight: a[i][j],
				}
				edges = append(edges, e)
			}
		}
	}
	sort.Slice(edges, func(i, j int) bool { return edges[i].weight < edges[j].weight })
	totalWeight := 0
	for _, edge := range edges {
		i := ElementKey(edge.i)
		j := ElementKey(edge.j)
		if sets.findSet(i) != sets.findSet(j) {
			totalWeight += edge.weight
			sets.union(i, j)
		}
	}
	fmt.Println(totalWeight)
}

Python: def main():
     def root(x):
          path=[]
          while x!=P[x]:
               path.append(x)
               x=P[x]
          for i in path:
               P[i]=x
          return x
     
     def is_same_set(x,y):
          return root(x)==root(y)
     
     def unite(x,y):
          P[root(x)]=root(y)
     
     n=int(input())
     P=[i for i in range(n)]
     edge_CostAndVertex=[]
     for i in range(n):
          cost=list(map(int,input().split()))
          for j in range(i):
               if cost[j]!=-1:
                    edge_CostAndVertex.append([cost[j],[i,j]])
                    
     edge_CostAndVertex.sort(key=lambda x:x[0])
     ans=0
     check=[]#連結されている頂点
     main_edge=edge_CostAndVertex[0][1][0]
     for i in edge_CostAndVertex:
          cost_i,a,b=i[0],i[1][0],i[1][1]
          if is_same_set(a,b):
               continue
          else:

               unite(a,b)
               ans+=cost_i
               if a not in check:
                    check.append(a)
               if b not in check:
                    check.append(b)
               if len(check)==n:
                    flag=1
                    for i in range(n):
                         for j in range(i):
                              if is_same_set(i,j):
                                   continue
                              else:
                                   flag=0
                                   break
                    if flag==1:
                         break
                    
     print(ans)
                    
if __name__=='__main__':
     main()

Python: # -*- coding: utf-8 -*-
"""
Created on Sat Jul 14 19:11:44 2018

@author: maezawa
"""

n = int(input())
m = []
for i in range(n):
    mi = list(map(int, input().split()))
    m.append(mi)

#print(*m, sep='\n')

color = [0]*n
d = [10**9]*n
p = [0]*n
p[0] = -1

def prim():
    while True:
        mincost = 10**9
        for i in range(n):
            if color[i] != 2 and d[i] < mincost:
                mincost = d[i]
                u = i
        if mincost == 10**9:
            break

        color[u] = 2

        for v in range(n):
            if color[v] != 2 and m[u][v] != -1:
                if m[u][v] < d[v]:
                    d[v] = m[u][v]
                    p[v] = u
                    color[v] = 1
    sumw = 0
    for i in range(n):
        if p[i] != -1:
            sumw += m[i][p[i]]
    return sumw

print(prim())

Python: def prim(n, M):
    color = [0 for _ in range(n)]
    d = [5000 for _ in range(n)]
    p = [-1 for _ in range(n)]

    d[0] = 0

    while True:
        mincost = 100000
        u = -1

        for i, dt in enumerate(d):
            if dt < mincost and color[i] != 1:
                mincost = dt
                u = i

        # ??´??°???????????£?????´???
        if mincost == 100000:
            break

        color[u] = 1

        for v in range(n):
            # ????????????, ?????????????¨???????????????¨??????
            if M[u][v] != 5000 and color[v] != 1:
                if M[u][v] < d[v]:
                    d[v] = M[u][v]
                    p[v] = u

    all_sum = 0

    for i, p_dt in enumerate(p):
        if p_dt != -1:
            all_sum += M[i][p_dt]

    return all_sum


def main():
    n = int(input())
    M = []

    for _ in range(n):
        dt = input().split(' ')
        M.append([5000 if int(d) == -1 else int(d) for d in dt])

    answer = prim(n, M)

    print(answer)

if __name__ == '__main__':
    main()

Python: n = int(input())
g = [[] for i in range(n)]
for i in range(n):
    *v, = map(int, input().split())
    for j in range(n):
        if v[j] < 0:
            v[j] = 10000
    g[i] = v

ans = 0
t = [0]
v = [i for i in range(1, n)]
while len(t) < n:
    u = [2000, 0, 0]
    for tv in t:
        for vv in v:
            if g[tv][vv] < u[0]:
                u = [g[tv][vv], tv, vv]
    ans += u[0]
    t.append(u[2])
    v.remove(u[2])
print(ans)

Python: n = int(input())
INFTY = 10**5
WHITE = 0
GRAY = 1
BLACK = 2

A = [[ int(row) if row != "-1" else INFTY for row in input().split()] for i in range(n)]

def prim(A, st):
    colors = [WHITE] * n
    colors[st] = BLACK
    T = [st]
    total_weights = 0
    
    while len(T) < n:
    
        current_min = INFTY
        next_add = st
        for node_inT in T:
            for v in range(n):
                if colors[v] == WHITE and A[node_inT][v] < current_min:
                    current_min = A[node_inT][v]
                    next_add = v

        total_weights += current_min
        T.append(next_add)
        colors[next_add] = BLACK
    
    return total_weights

MST = [0] * n
for i in range(n):
    MST[i] = prim(A, i)

print(min(MST))

Python: from __future__ import division, print_function
from sys import stdin, maxint
 
 
def main():
    num = int(stdin.readline())
 
    y = []
    for _ in xrange(num):
        it = iter(int(s) for s in stdin.readline().split()[1:])
        y.append([(next(it), next(it)) for _ in xrange(next(it))])
    weight = [maxint] * num
    weight[0] = 0
    t = set(xrange(1, num))
    index = 0
 
    while t:
        for v, cost in y[index]:
            if v not in t:
                continue
            weight[v] = min(weight[v], cost + weight[index])

        index = min(t, key=lambda i: weight[i])
        t.remove(index)

    for i, d in enumerate(weight):
        print(i, d)
 
 
main()