Go: package main

import (
	"fmt"
	"sort"
)

type Edge struct {
	I int
	J int
	A int
}

func main() {
	var n int
	fmt.Scan(&n)

	g := make([][]int, n)
	edges := make([]Edge, 0, n*(n-1)/2)
	parents := make([]int, n)
	for i := 0; i < n; i++ {
		g[i] = make([]int, n)
		for j := 0; j < n; j++ {
			fmt.Scan(&g[i][j])
			if g[i][j] >= 0 {
				edges = append(edges, Edge{i, j, g[i][j]})
			}
		}
		parents[i] = i
	}
	sort.SliceStable(edges, func(i, j int) bool { return edges[i].A >= edges[j].A })

	sum := 0
	num := 0
	for len(edges) > 0 && num < n-1 {
		edge := edges[len(edges)-1]
		edges = edges[:len(edges)-1]

		if same(edge.I, edge.J, &parents) {
			continue
		}
		union(edge.I, edge.J, &parents)
		sum += edge.A
		num += 1
	}
	fmt.Println(sum)
}



func root(id int, parents *[]int) int {
	if id == (*parents)[id] {
		return id
	}
	return root((*parents)[id], parents)
}

func union(i, j int, parents *[]int) {
	(*parents)[root(j, parents)] = (*parents)[root(i, parents)]
}

func same(i, j int, parents *[]int) bool {
	return root(i, parents) == root(j, parents)
}

Python: #!/usr/bin/env python
from __future__ import division, print_function
from sys import stdin, maxint


def main():
    num = int(stdin.readline())

    M = []
    for _ in xrange(num):
        M.append([int(s) for s in stdin.readline().split()])

    g = set(xrange(1, num+1))
    index = g.pop()
    h = {index}
    gravity = 0

    while g:
        minimum = maxint
        for j in h:
            for i, a in enumerate(M[j-1], 1):
                if i in h:
                    continue
                if 0 < a < minimum:
                    index = i
                    minimum = a
        h.add(index)
        g.remove(index)
        gravity += minimum

    print(gravity)


main()

Python: n = int(input())
edge = []
for i in range(n):
    a = list(map(int, input().split()))
    for j in range(i + 1, n):
        if a[j] != -1:
            edge.append((a[j], i, j))
edge.sort()
ans = 0

tree = [i for i in range(n)]
def root(x):
    pre = []
    while x != tree[x]:
        pre.append(x)
        x = tree[x]
    for node in pre:
        tree[node] = x
    return x
def unite(x, y):
    X, Y = root(x), root(y)
    if X != Y:
        tree[X] = Y

for cost, x, y in edge:
    X, Y = root(x), root(y)
    if X != Y:
        ans += cost
        tree[X] = Y
print(ans)

Python: import sys
input = sys.stdin.readline
from operator import itemgetter
sys.setrecursionlimit(10000000)
INF = 10**30
M = []

def prim(G, root, n):
    BLACK = 1<<10
    WHITE = 1<<20
    nodes = [WHITE] * n
    d = [INF] * n
    d[root] = 0
    p = [0] * n
    p[root] = -1
    while True:
        mincost = INF

        # 探索
        for i in range(n):
            if d[i] < mincost and nodes[i] == WHITE:
                mincost = d[i]
                next = i
        if mincost == INF:
            break
        # 移動
        nodes[next] = BLACK

        # 伝播
        for i in range(n):
            if nodes[i] == WHITE and G[next][i] != INF:
                if G[next][i] < d[i]:
                    d[i] = G[next][i]
                    p[i] = next
    return d

def main():
    global M
    n = int(input().strip())
    M = [[0] * n for _ in range(n)]
    for i in range(n):
        M[i] = list(map(lambda x: INF if x == -1 else x, map(int, input().strip().split())))
    d = prim(M, 0, n)
    print(sum(d))

if __name__ == '__main__':
    main()

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()