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: # -*- coding: utf-8 -*-
from heapq import heappop, heappush


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 (adj_matrix=False) (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 (adj_matrix=True)
    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)

    costs = [float('inf')] * n
    costs[start] = 0
    prevs = [-1] * n

    pq = [(0, start)]
    T = [True] * n

    while pq:
        tmp_cost, tmp_node = heappop(pq)
        T[tmp_node] = False

        nxt_edges = ((node, cost) for node, cost in enumerate(edges[tmp_node]) if cost != default_value and T[node]) if adj_matrix else\
                    ((node, cost) for node, cost in edges[tmp_node] if T[node])

        for nxt_node, nxt_cost in nxt_edges:
            if costs[nxt_node] > nxt_cost:
                costs[nxt_node] = nxt_cost
                prevs[nxt_node] = tmp_node
                heappush(pq, (nxt_cost, nxt_node))
                T[nxt_node] = True

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

        else:
            return prevs, costs


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)]

    prevs, costs = prim(edges)
    print(sum(costs))

Python: import sys

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 solve():
    n = int(input())
    edges = []

    for i in range(n):
        line = [int(j) for j in input().split()]
        edges += [e for e in line[i + 1:] if e >= 0]

    edges.sort()
    ans = sum(edges[:n - 1])

    print(ans)

if __name__ == '__main__':
    solve()

Python: n=int(input())
edgeList=[]
for i in range(n):
 a=list(map(int,input().split()))
 for j in range(i):
  if a[j]>0:edgeList+=[[a[j],i,j]]
rootList=[-1]*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: from sys import stdin
INF = 1<<21
WHITE = 0
GRAY = 1
BLACK = 2
n = int(stdin.readline())
M = [[INF] * (n + 1) for _ in range(n + 1)]
for i in range(0, n):
    for j, e in enumerate(list(map(int, stdin.readline().split()))):
        if e != -1: M[i][j] = e
d = [INF] * n
d[0] = 0
t = [-1] * n
color = [0] * n
def prim():
    while True:
        minv = INF
        u = -1
        for i in range(0, 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(0, n):
            if color[v] != BLACK and d[v] > M[u][v]:
                d[v] = M[u][v]
                t[v] = u
                color[v] = GRAY
    return sum(d)
print(prim())

Python: def main():

    N = 100

    n = int(input())
    adj = [[0 for i in range(n)] for j in range(n)]

    for i in range(n):
        tmp = list(map(int, input().split()))
        u = tmp[0]
        u = u -1
        k = tmp[1]
        v = tmp[2:]
        for j in range(k):
            adj[u][v[j]-1] = 1
            print(adj)

    for i in range(n):
        for j in range(n):
            print(adj[i][j], end=" ")
        print()

if __name__ == "__main__":
    main()

Python: n=int(input())
m=[list(map(int,input().split()))for _ in[0]*n]
# m = [[-1 for i in range(n)] for j in range(n)]
d=[0]+[10**9]*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: 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()

Python: M=[]
n=int(input())
for i in range(n):
	b=list(map(int,input().split()))
	M.append(b)
ans=0
from copy import copy
t=[0]
dis=copy(M[0])
dis[0]=10**12
for i in range(n):
	if dis[i]==-1:
		dis[i]=10**10
for i in range(n-1):
	p=10**10
	for j in range(n):
		if dis[j]<p:
			p=dis[j]
			q=j
	ans+=p
	t.append(q)
	dis[q]=10**12
	for j in range(n):
		if dis[j]>M[j][q] and M[j][q]!=-1 and dis[j]!=10**12:
			dis[j]=M[j][q]
print(ans)