Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

const INF = 1 << 60

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N := sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < N; i++ {
		G[i] = make([]int, N)
		for j := 0; j < N; j++ {
			G[i][j] = sc.nextInt()
		}
	}
	d := make([]int, N)
	for i := 0; i < N; i++ {
		d[i] = INF
	}
	seen := make([]bool, N)
	d[0] = 0
	ans := 0
	for {
		cur := 0
		minCost := INF
		for i := 0; i < N; i++ {
			if !seen[i] && d[i] < minCost {
				minCost = d[i]
				cur = i
			}
		}
		if minCost == INF {
			break
		}
		seen[cur] = true
		ans += d[cur]
		for i := 0; i < N; i++ {
			cost := G[cur][i]
			if cost != -1 && cost < d[i] {
				d[i] = cost
			}
		}
	}

	fmt.Fprintln(wtr, ans)
	wtr.Flush()
}

Python: n = int(input())
edgeList = []
for i in range(n):
    a = list(map(int, input().split()))
    for j in range(i):
        if a[j] != -1:
            edgeList.append([a[j], i, j])
rootList = [-1 for i in range(n)]
sumLength = 0

def getRoot(x):
    r = rootList[x]
    if r < 0:
        rootList[x] = x
    elif r != x:
        rootList[x] = getRoot(r)
    return rootList[x]
        

edgeList.sort(key=lambda x: x[0])
for e in edgeList:
    x = getRoot(e[1])
    y = getRoot(e[2])
    if x != y:
        sumLength += e[0]
        rootList[x] = rootList[y] = min(x, y)
print(sumLength)

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


n = int(raw_input())
A = [0] * n
for u in range(n):
    A[u] = map(int, raw_input().split())
 
result = prim(A)
print(result)

Python: #ALDS1_12_A Minimum Spanning Tree
import sys


n = int(input())
G = []
for i in range(n):
    input_list = list(map(int, sys.stdin.readline().strip().split()))
    adj = [j if j != -1 else float('inf') for j in input_list]
    adj[i] = 0
    G.append(adj)

p = ['unexplored'] * n  # 親を保存するリスト
d = [float('inf')] * n  # 距離を保存するリスト

p[0] = 0
d[0] = 0
u = 0

for _ in range(n):
    mincost = float('inf')
    for i in range(n):
        if (p[i] == 'unexplored') & (d[i] < mincost):
            mincost = d[i]
            u = i  # u is child

    for i in range(n):
        if (p[i] != 'unexplored') & (G[i][u] == mincost):
            p[u] = i
            break
            
    for i in range(n):
        if G[u][i] < d[i]:
            d[i] = G[u][i]
    # print(p)

ans = 0
for i in range(1, n):
    ans += G[p[i]][i]
print(ans)

Python: n=int(input())

ds=[i for i in range(n)]
def root(x):
  path_to_root = []
  while ds[x] != x:
    path_to_root.append(x)
    x = ds[x]
  for i in path_to_root:
    ds[i] = x
  return x
def same(x,y):
  return root(x) == root(y)
def unite(x,y):
  ds[root(x)] = root(y)

p=[] #[a,i,j]:i<j
for i in range(n):
  a=list(map(int,input().split()))
  for j in range(i+1,n):
    if a[j]!=-1: p.append([a[j],i,j])
p.sort(key=lambda x:x[0])
ans=0
for i in p:
  if same(i[1],i[2]): continue
  unite(i[1],i[2])
  ans+=i[0]
print(ans)

Python: INFTY = 1 << 21
WHITE = 0
GRAY = 1
BLACK = 2

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

d = [INFTY for i in range(n)]
p = [-1 for i in range(n)]
color = [WHITE 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: from sys import stdin

def read_matrix(n):
    A = []
    for _ in range(n):
        a = [ int(i) for i in stdin.readline().strip().split() ]
        A.append(a)
    return A

def prim(n, A):
    color = [ 'WHITE' for i in range(n) ]
    d = [ float('inf') for i in range(n) ]
    d[0] = 0
    p = [-1] * n

    while True:
        mincost = float('inf')
        for i in range(n):
            if color[i] != 'BLACK' and d[i] < mincost:
                mincost = d[i]
                u = i

        if mincost == float('inf'):
            break

        color[u] = 'BLACK'

        for v in range(n):
            if color[v] != 'BLACK' and A[u][v] != -1:
                if A[u][v] < d[v]:
                    d[v] = A[u][v]
                    p[v] = u
                    color[v] = 'GRAY'

    return sum(d)

n = int(input())
A = read_matrix(n)
print(prim(n, A))

Python: def prim():
    distance[0] = 0
    parent[0] = -1

    while True:
        mincost = float('inf')
        for i in range(n):
            if color[i] != 'black' and distance[i] < mincost:
                mincost = distance[i]
                u = i
        if mincost == float('inf'):
            break

        color[u] = 'black'

        for v in range(n):
            if color[v] != 'black' and adjMat[u][v] != float('inf'):
                if adjMat[u][v] < distance[v]:
                    distance[v] = adjMat[u][v]
                    parent[v] = u
                    color[v] = 'gray'


n = int(input())
color = ['white'] * n
parent = [-1] * n
distance = [float('inf')] * n

adjMat = [[0] * n for _ in range(n)]
for i in range(n):
    adjRow = list(map(int, input().split()))
    for v, weight in enumerate(adjRow):
        if weight == -1:
            adjMat[i][v] = float('inf')
        else:
            adjMat[i][v] = weight

prim()

print(sum(distance))