Go: package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)

	g := make([][]int, n)
	ans := make([][]int, n)

	inf := 1 << 30
	for i := 0; i < n; i++ {
		g[i] = make([]int, n)
		ans[i] = make([]int, n)
		for ii := 0; ii < n; ii++ {
			g[i][ii] = getNextInt(scanner)
			if g[i][ii] == -1 {
				g[i][ii] = inf
			}
			ans[i][ii] = -1
		}
	}

	im := make(IntMap, 1)

	im.increment(1)

	for len(im) < n {
		min := inf
		u := -1
		v := -1
		for i := range im {
			for ii := 0; ii < n; ii++ {
				if im.get(ii) != 0 {
					continue
				}
				if min > g[i][ii] {
					min = g[i][ii]
					u = i
					v = ii
				}
			}
		}
		im.increment(v)
		ans[u][v] = min
		ans[v][u] = min
	}

	sum := 0
	for i := 0; i < n-1; i++ {
		for ii := i + 1; ii < n; ii++ {
			if ans[i][ii] != -1 {
				sum += ans[i][ii]
			}
		}
	}

	fmt.Fprintln(writer, sum)
	writer.Flush()
}

// IntMap ...
type IntMap map[int]int

func (m IntMap) get(key int) int {
	if _, ok := m[key]; ok {
		return m[key]
	}
	return 0
}
func (m IntMap) increment(key int) {
	if _, ok := m[key]; ok == false {
		m[key] = 0
	}
	m[key]++
}

Python: N = int(input())

#M[u][v]:uからvへの重みを保存した隣接行列
M=[]
for n in range(N):
    input_temp = list(map(int,input().split()))
    M.append(input_temp)

#color:各頂点の訪問状態を示す
color=['white']*N

#d:TとV-Tを繋ぐ辺の中で重みが最小の辺の重みの値を保持
d=[10**10]*N

#p[v-1]:MSTにおけるvの親を保持
p=[-1]*N

#初期値
d[0] = 0
p[0] = -1

# ans=0
while True:
#     ans+=1
    mincost=10**10
    for i in range(N):
        if color[i] != 'BLACK' and d[i] < mincost:
            mincost = d[i]
            u = i
#     print(u,mincost)       
    if mincost == 10**10:
        break
    
    color[u] = 'BLACK'
    
    for v in range(N):
        if color[v] != 'BLACK' and M[u][v]!=-1:
#             print(u,v,color[v],M[u][v],d[v])
            if M[u][v] < d[v]:
                d[v] = M[u][v]
                p[v] = u
                color[v] = 'GRAY'
#     print(color,mincost,d,p)
    
print(sum(d))

Python: # -*- coding: utf-8 -*-
def prim(edges, *, start=0, adj_matrix=False, default_value=float('inf')):
    '''
    Returns the Minimum Spanning Tree(MST) of a given graph

    # sample input when given not as adjacency list (generally works faster)
    edges = [[(1, 2), (2, 5), (3, 4)],         # node 0
             [(0, 2), (3, 3), (4, 6)],         # node 1
             [(0, 5), (3, 2), (5, 6)],         # node 2
             [(0, 4), (1, 3), (2, 2), (4, 2)], # node 3
             [(1, 6), (3, 2), (5, 4)],         # node 4
             [(2, 6), (4, 4)]]                 # node 5

    # sample input when given as adjacency matrix
    edges = [[0, 2, 5, 4, inf, inf],           # node 0
             [2, 0, inf, 3, 6, inf],           # node 1
             [5, inf, 0, 2, inf, 6],           # node 2
             [4, 3, 2, 0, 2, inf],             # node 3
             [inf, 6, inf, 2, 0, 4],           # node 4
             [inf, inf, 6, inf, 4, 0]]         # node 5
    '''

    n = len(edges)
    mst = []
    cost = 0
    T = [start]

    while True:
        tmp_edges = [(cost, (u, v)) for u in T for v, cost in enumerate(edges[u]) if cost != default_value and v not in T] if adj_matrix else\
                    [(cost, (u, v)) for u in T for v, cost in edges[u] if v not in T]

        if tmp_edges:
            min_cost, min_edge = min(tmp_edges)
            mst.append(min_edge)
            cost += min_cost
            T.append(min_edge[1])

        else:
            if len(mst) != n - 1:
                raise NoSpanningError(
                    'There is no spanning tree in this graph (search started from node{})'.
                    format(start))

            else:
                return mst, cost


class NoSpanningError(Exception):
    pass


if __name__ == '__main__':
    '''
    an example of using this function
    AIZU ONLINE JUDGE - ALDS_1_12_A
    '''

    n = int(input())
    edges = [[(j, int(cost)) for j, cost in enumerate(input().split()) if int(cost) != -1] for i in range(n)]

    print(prim(edges)[1])

Python: import sys
# sys.stdin = open('input.txt')

def createMatrix():
  matrix = [[i for i in map(int, input().split())] for i in range(n)]
  return matrix

def prim():
    d[0] = 0
    p[0] = -1

    while True:
        mincost = INFTY
        for i in range(n):
            if status[i] != VISITED and d[i] < mincost:
                mincost = d[i]
                u = i

        if mincost == INFTY:
            break

        status[u] = VISITED

        for v in range(n):
            if status[v] != VISITED and matrix[u][v] != -1:
                if matrix[u][v] < d[v]:
                    d[v] = matrix[u][v]
                    p[v] = u
                    status[v] = VISITING

n = int(input())
NOT_VISITED = 0 # WHITE
VISITING = 1 # GRAY
VISITED = 2 # BLACK
INFTY = 10**21

matrix = createMatrix()
status =  [NOT_VISITED] * n
d = [INFTY] * n
p = [-1] * n

prim()
print(sum(d))

Python: import heapq
from collections import defaultdict
v_num = int(input())
edges = defaultdict(list)
for i in range(v_num):
    data = [int(n) for n in input().split(" ")[1:]]
    for j in range(i + 1, v_num):
        if data[j] != -1:
            edges[i].append([data[j], j])
            edges[j].append([data[j], i])
queue = []
heapq.heapify(queue)
for c in edges[0]:
    heapq.heappush(queue, c)
visited = {0}
answer = 0
while len(visited) < v_num:
    q = heapq.heappop(queue)
    weight, one = q[0], q[1]
    if one in visited:
        continue
    answer += weight
    for e in edges[one]:
        heapq.heappush(queue, e)
    visited |= {one}
print(answer)

Python: n = int(input())
G = []
for i in range(n):
    G.append(input().split())
    for j in range(len(G[i])):
        G[i][j] = int(G[i][j])

ans = 0
mincost = [2001] * n
flag = [0] * n
mincost[0] = 0
while True:
    v = -1
    for j in range(n):
        if flag[j] != 1 and (v == -1 or mincost[j] < mincost[v]):
            v = j
    if v == -1:
        break
    flag[v] = 1
    ans += mincost[v]
    for j in range(n):
        if G[v][j] == -1: continue
        mincost[j] = min(mincost[j], G[v][j])

print(ans)

Python: n = int(input())
G = [[int(i) for i in input().split()] for i in range(n)]

S = set([])
for i,row in enumerate(G):
    for j,col in enumerate(row):
        if col != -1:
            k = tuple(sorted([i,j]))
            S.add(k + (col, ))

rank = {}
p = {}

def makeSet(x):
    p[x] = x
    rank[x] = 0

def link(x, y):
    if  rank[x] > rank[y]:
        p[y] = x
    else:
        p[x] = y
    if  rank[x] == rank[y]:
        rank[y] += 1

def union(x, y):
    link(findSet(x), findSet(y))
    
def findSet(x):
    if  x != p[x]:
        p[x] = findSet(p[x])
    return p[x]
    
def isSameSet(x, y):
    return findSet(x) == findSet(y)

def kruskal(G, n, S):
    ret = 0
    for x in range(n):
        makeSet(x)
    while len(S) != 0:
        u, v, c = min(S, key=lambda x: x[2])
        S = S - set([(u,v,c)])
        if not isSameSet(u, v):
            union(u, v)
            ret += c
    return ret
print(kruskal(G, n, S))