Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() int {
	n, err := strconv.Atoi(nextString())
	if err != nil {
		fmt.Printf("strconv.Atoi failed: %v\n", err)
	}
	return n
}

type ElementKey int
type Node struct {
	key    ElementKey
	parent *Node
	rank   int
}

func newNode(key ElementKey) *Node {
	node := Node{}
	node.key = key
	node.parent = &node
	node.rank = 0

	return &node
}

func union(x, y *Node) {
	xSet := findSet(x)
	ySet := findSet(y)
	link(xSet, ySet)
}

func link(x, y *Node) {
	if x.rank > y.rank {
		y.parent = x
	} else {
		x.parent = y

		if x.rank == y.rank {
			y.rank++
		}
	}
}

func findSet(x *Node) *Node {
	if x != x.parent {
		x.parent = findSet(x.parent)
	}
	return x.parent
}

func newDisjointSets(nSets int) *DisjointSets {
	sets := DisjointSets{}
	sets.keyToNode = map[ElementKey]*Node{}
	for i := 0; i < nSets; i++ {
		key := ElementKey(i)
		sets.keyToNode[key] = newNode(key)
	}
	return &sets
}

type DisjointSets struct {
	keyToNode map[ElementKey]*Node
}

func (sets *DisjointSets) union(x, y ElementKey) {
	xNode := sets.keyToNode[x]
	yNode := sets.keyToNode[y]
	union(xNode, yNode)
}

func (sets DisjointSets) findSet(x ElementKey) *Node {
	xNode := sets.keyToNode[x]
	return findSet(xNode)
}

type Edge struct {
	i, j   int
	weight int
}

func main() {
	scanner.Split(bufio.ScanWords)

	n := nextInt()
	sets := newDisjointSets(n)
	edges := []Edge{}
	a := make([][]int, n)
	for i := 0; i < n; i++ {
		a[i] = make([]int, n)
		for j := 0; j < n; j++ {
			a[i][j] = nextInt()
			if a[i][j] >= 0 {
				e := Edge{
					i:      i,
					j:      j,
					weight: a[i][j],
				}
				edges = append(edges, e)
			}
		}
	}
	sort.Slice(edges, func(i, j int) bool { return edges[i].weight < edges[j].weight })
	totalWeight := 0
	for _, edge := range edges {
		i := ElementKey(edge.i)
		j := ElementKey(edge.j)
		if sets.findSet(i) != sets.findSet(j) {
			totalWeight += edge.weight
			sets.union(i, j)
		}
	}
	fmt.Println(totalWeight)
}

Python: # -*- coding: utf-8 -*-
'''
所要時間は、分位であった。
'''
# ライブラリのインポート
#import re #正規表現
import sys
#import heapq
import bisect
#import collections
#import math

def main():
    n = int(input())
    X = [[] for i in range(n)]
    l = []
    for i, line in enumerate(sys.stdin):
        X[i] = list(line.strip("\n").split())
        for j in range(i,n):
            c = int(X[i][j])
            if c == -1:
                continue
            else:
                r = (c,i,j)
                bisect.insort(l, r)
    
    uf = UnionFind(n)
    k = 0
    ans = 0
    count = 0
    while(count < n):
        try: tmp = l[k]
        except: break
        x = tmp[1]
        y = tmp[2]
        if not uf.same(x,y):
            uf.unite(x, y)
            ans += tmp[0] 
            count += 0
        k += 1
    print(ans)

class UnionFind:
    def __init__(self,n):
        self.p = [i for i in range(n)]
        return
    
    def root(self,x):
        while(1):
            if (self.p[x] == x): break
            y = x
            x = self.p[x]
            self.p[y] = self.p[x]
        return x

    def unite(self ,x, y):
        rx = self.root(x)
        ry = self.root(y)
        if rx == ry: return
        else:
            self.p[rx] = ry
            return 
    
    def same(self, x, y):
        rx = self.root(x)
        ry = self.root(y)
        return rx == ry


    
if __name__ == '__main__':
    main()

Python: # -*- coding: utf-8 -*-
"""
Created on Sat Sep 22 11:44:37 2018
ALDS1-12-A
@author: maezawa
"""
import heapq

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

adj = [[] for _ in range(n+1)]
for i in range(n):
    for j in range(i, n):
        if amat[i][j] == -1:
            continue
        adj[i+1].append([amat[i][j], j+1])
        adj[j+1].append([amat[j][i], i+1])

#print(adj)
d = [10**10]*(n+1)
h = []
heapq.heappush(h, [0, 1]) # [cost, node]
visited = [False]*(n+1)
while h:
    cost, node = heapq.heappop(h)
    if visited[node] == False and cost < d[node]:
        d[node] = cost
        visited[node] = True
        for nextnode in adj[node]:
            if visited[nextnode[1]]:
                continue
            heapq.heappush(h,nextnode)

d.pop(0)
print(sum(d))

Python: MAX = 2001


def prim(tree: [int], adjacent_list: [[int]]):
    cost = 0
    next = 0
    for l in adjacent_list:
        l[next] = MAX
    while True:
        tree.append(next)
        min_list = list()
        for t in tree:
            min_list.append(min([(v, i) for i, v in enumerate(adjacent_list[t])]))
        min_cost, i = min(min_list)
        if min_cost == MAX:
            return cost
        cost += min_cost
        for l in adjacent_list:
            l[i] = MAX
        next = i


if __name__ == '__main__':
    N = int(input())
    adjacent_list = [[int(e) if int(e) != -1 else MAX for e in input().rstrip().split()] for _ in range(N)]
    test_list = []
    print(prim(test_list, adjacent_list))

Python: n=int(input())
m = [[-1 for i in range(n)] for j in range(n)]
for i in range(n): #隣接の辺のコストを入力
  nums = list(map(int, input().split()))
  for j in range(n):
    m[i][j] = nums[j]

d=[0]+[10**9]*n
visited=[0]*n
a=0
while 1:
  u=-1
  for i in range(n):
    if not visited[i] and (u<0 or d[i]<d[u]):
      u=i
  if u<0:
    break
  visited[u]=1
  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: n = int(input())
A = []
for i in range(n):
    line = input()
    A.append([int(x) for x in line.split()])

V = set(range(n))
Vnew = {0}  # ??¨???????°???¨?????????
weight = 0

while V != Vnew:
    T = V - Vnew
    minw = float('inf')
    for u in Vnew:
        for v in T:
            w = A[u][v]
            if w != -1:
                e = (u, v)
                minw = min(minw, w)
    Vnew.add(e[1])
    weight += minw


print(weight)

Python: import sys
input = sys.stdin.readline
INF = 100100

def prim(n: int, M: list):
    ans = 0
    visited = [False] * n
    d = [INF] * n
    p = [-1] * n
    d[0] = 0
    while True:
        mincost = INF
        for i in range(n):
            if not visited[i] and d[i] < mincost:
                mincost = d[i]
                u = i
        if mincost == INF:
            break
        ans += mincost
        visited[u] = True
        for v in range(n):
            if not visited[v] and M[u][v] != -1:
                if M[u][v] < d[v]:
                    d[v] = M[u][v]
                    p[v] = u
    return ans

def main():
    n = int(input())
    M = []
    for _ in range(n):
        Mi = list(map(int, input().split()))
        M.append(Mi)
    ans = prim(n,M)
    print(ans)

if __name__ == '__main__': main()

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():
    inf = float('inf')
    n = int(input())
    a = []

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

    
    checked = [False] * n
    d = [inf] * n
    d[0] = 0
    checked[0] = True
    ans = 0
    nxt = 0

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

        min_w = inf
        min_n = 0

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

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

    # debug(d, locals())
    print(ans)



if __name__ == '__main__':
    solve()