Go: package main

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

//util
var sc = bufio.NewScanner(os.Stdin)

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

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func printList(list []int) {
	n := len(list)
	buf := bufio.NewWriter(os.Stdout)
	for _, v := range list[0 : n-1] {
		buf.Write([]byte(fmt.Sprintf("%d ", v)))
	}
	buf.Write([]byte(fmt.Sprintf("%d\n", list[n-1])))
	buf.Flush()
}

func max(a, b int) int {
	if a > b {
		return a
	} else {
		return b
	}
}

func min(a, b int) int {
	if a > b {
		return b
	} else {
		return a
	}
}

//solve
const (
	MAX   = 100
	INFTY = (1 << 21)
	WHITE = 0
	GRAY  = 1
	BLACK = 2
)

//V: グラフの頂点全体の集合
//T: MSTに属する頂点の集合
var (
	n     int
	M     [MAX][MAX]int //重みを記録する隣接行列
	color [MAX]int
	p     [MAX]int //MSTにおける頂点の親を記録
	d     [MAX]int //Tに属する頂点と、V−Tに属する頂点を繋ぐ辺の中で、重みが最小のものを記録
)

func prim() int {
	var u, minv int
	//初期化
	for i := 0; i < n; i++ {
		d[i] = INFTY
		p[i] = -1
		color[i] = WHITE
	}

	d[0] = 0

	for {
		//頂点uを決めていく
		//つまり、Tに属する頂点と、V−Tに属する頂点を繋ぐ辺の中で、重みが最小のものを決める
		minv = INFTY
		u = -1
		for i := 0; i < n; i++ {
			//未訪問かつ、辺の重みが最小となるuを選ぶ
			if minv > d[i] && color[i] != BLACK {
				u = i
				minv = d[i]
			}
		}

		if u == -1 {
			break
		}

		color[u] = BLACK
		for v := 0; v < n; v++ {
			//未訪問かつ、辺が存在するとき
			if color[v] != BLACK && M[u][v] != INFTY {
				if d[v] > M[u][v] {
					d[v] = M[u][v]
					p[v] = u
					color[v] = GRAY
				}
			}
		}
	}

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

func main() {
	sc.Split(bufio.ScanWords)
	n = nextInt()

	for i := 0; i < n; i++ {

		for j := 0; j < n; j++ {
			tmp := nextInt()
			if tmp == -1 {
				tmp = INFTY
			}
			M[i][j] = tmp
		}

	}

	fmt.Println(prim())

}

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)

Python: from heapq import heappush, heappop, heapify

n = int(input())
g = [[] for _ in range(n)]

for i in range(n):
    for j,k in enumerate(map(int,input().split())):
        if k != -1:
            g[i].append((j,k))
#    print(g[i])

ocupied = [0]*n
que = [(j,k) for k,j in g[0]] # 重み、子の順番
#print(f'g[0]: {g[0]}')　#子、重みの順番
#print(f'que: {que}')
ocupied[0] = 1
heapify(que)

ans = 0
while que:
    cv,v = heappop(que)
    #print(f'cv, v: {cv}, {v}')
    if ocupied[v]: # vは頂点　どこでvが頂点になるか
        continue
    ocupied[v] = 1
    ans += cv
    for j,k in g[v]:
        if ocupied[j]:
            continue
        heappush(que,(k,j))
    #print(f'ocupied: {ocupied}')
print(ans)

Python: import sys, os, math, bisect, itertools, collections, heapq, queue, copy, array

# from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall
# from decimal import Decimal
# from collections import defaultdict, deque

sys.setrecursionlimit(10000000)

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: (x * y) // math.gcd(x, y)

MOD = 10 ** 9 + 7
INF = float('inf')


class UnionFind:
    def __init__(self, N):
        self.tree = list(range(N))

    def root(self, N):
        if self.tree[N] == N:
            return N
        else:
            self.tree[N] = self.root(self.tree[N])
            return self.tree[N]

    def same(self, x, y):
        return self.root(self.tree[x]) == self.root(self.tree[y])

    def unite(self, x, y):
        x = self.root(x)
        y = self.root(y)
        if x == y:
            return
        else:
            self.tree[x] = y


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    N = ii()
    uf = UnionFind(N)
    ret = 0
    cost = []
    for i in range(N):
        D = il()
        for j in range(N):
            if D[j] != -1:
                cost.append((D[j], i, j))
    else:
        cost.sort()
        for c, v1, v2 in cost:
            if not uf.same(v1, v2):
                ret += c
                uf.unite(v1, v2)
        print(ret)


if __name__ == '__main__':
    main()

Python: import sys

inf = float('inf')

def debug(x, table):
    for name, val in table.items():
        if x is val:
            print('DEBUG:{} -> {}'.format(name, val), file=sys.stderr)
            return None

def prim(n, As):
    checked = [False] * n
    d = [inf] * n
    checked[0] = True
    d[0] = 0
    nxt = 0
    tot_wgt = 0

    for i in range(n - 1):
        for j in range(n):
            if As[nxt][j] < d[j]:
                d[j] = As[nxt][j]

        min_w = inf
        min_n = 0
        for j in range(n):
            if not checked[j] and min_w > d[j]:
                min_w = d[j]
                min_n = j

        tot_wgt += min_w
        nxt = min_n
        checked[nxt] = True

    return tot_wgt

def solve():
    n = int(input())
    As = []

    for i in range(n):
        line = [int(j) for j in input().split()]
        As.append([i if i != -1 else inf for i in line])

    ans = prim(n, As)

    print(ans)


if __name__ == '__main__':
    solve()

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)