Go: package main

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

const (
	MAX_N      = 200
	MAX_WEIGHT = 2000
)

type Edge struct {
	start  int
	end    int
	weight int
}

type ShortestInfo struct {
	edges    []Edge
	shortest int
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}

	shortestList := make([]ShortestInfo, n)
	for i := 1; i < n; i++ {
		shortestList[i] = ShortestInfo{edges: []Edge{}, shortest: MAX_N*MAX_WEIGHT + 1}
	}

	adjacentMatrix := make([][]int, n)
	for i := 0; i < n; i++ {
		adjacentMatrix[i] = make([]int, n)
		for j := 0; j < n; j++ {
			v, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			adjacentMatrix[i][j] = v
		}
	}

	mst([]int{1}, shortestList, adjacentMatrix)
	fmt.Println(calculateMinWeight(shortestList))
}

func calculateMinWeight(shortestList []ShortestInfo) int {
	visitedList := make([]bool, len(shortestList))
	visitedList[0] = true
	sumWeight := 0
	for !visitedAll(visitedList) {
		shortestInfo := shortestList[0]
		shortestList = shortestList[1:]
		edges := shortestInfo.edges
		for _, edge := range edges {
			if !visitedList[edge.end-1] {
				visitedList[edge.end-1] = true
				sumWeight += edge.weight
			}
		}
	}
	return sumWeight
}

func visitedAll(visitedList []bool) bool {
	for _, v := range visitedList {
		if !v {
			return false
		}
	}
	return true
}

func mst(nodeStack []int, shortestList []ShortestInfo, adjacentMatrix [][]int) {
	for len(nodeStack) > 0 {
		currentNode := nodeStack[0]
		nodeStack = nodeStack[1:]
		currentShortest := getShortest(currentNode, shortestList)
		adjacents := findAdjacents(currentNode, adjacentMatrix)
		for i := 0; i < len(adjacents); i++ {
			adj := adjacents[i]
			s := getShortest(adj.end, shortestList)
			if currentShortest.shortest+adj.weight < s.shortest || (currentShortest.shortest+adj.weight == s.shortest && len(currentShortest.edges)+1 > len(s.edges)) {
				setShortest(adj.end, adj, currentShortest, shortestList)
				nodeStack = append(nodeStack, adj.end)
			}
		}
	}
}

func getShortest(node int, shortestList []ShortestInfo) ShortestInfo {
	return shortestList[node-1]
}

func setShortest(node int, edge Edge, currentShortest ShortestInfo, shortestList []ShortestInfo) {
	newEdges := make([]Edge, len(currentShortest.edges)+1)
	for i := 0; i < len(newEdges)-1; i++ {
		newEdges[i] = currentShortest.edges[i]
	}
	newEdges[len(newEdges)-1] = edge
	shortestInfo := ShortestInfo{edges: newEdges, shortest: currentShortest.shortest + edge.weight}
	shortestList[node-1] = shortestInfo
}

func findAdjacents(currentNode int, adjacentMatrix [][]int) []Edge {
	adjacents := adjacentMatrix[currentNode-1]
	edges := []Edge{}
	for i, v := range adjacents {
		if v > 0 {
			edges = append(edges, Edge{start: currentNode, end: i + 1, weight: v})
		}
	}
	return edges
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

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))

Python: n = int(input())
a = []

for i in range(n):
    inp = input()
    if "-1" in inp:
        inp = inp.replace("-1","10000")
    a.append(list(map(int, inp.split())))

w = 0
v = set()
v.add(0)

while len(v) < n:
    print(v)
    min_w   = 10000
    min_idx = 0
    i = 0
    for node in v:
        if min_w > min(a[node]):
            min_w = min(a[node])
            i = node
            min_idx = a[i].index(min_w)
    if min_idx in v:
        a[i][min_idx] = 10000
        continue
    else:
        w += min_w
        v.add(min_idx)

print(w)

Python: n = int(input())
edgeList = []
for i in range(n):
    a = list(map(int, input().split()))
    for j in range(i):
        if a[j] != -1:
            edgeList.append([a[j], i, j])
rootList = [-1 for i in range(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: def prim(cost):
    sumcost = 0
    V = len(cost)
    mincost = [float('inf')] * V
    used = [False] * V
    mincost[0] = 0
    while True:
        v = -1
        for u in range(V):
            if not used[u] and (v == -1 or mincost[u] < mincost[u]):
                v = u
        if v == -1: break
        used[v] = True
        sumcost = sumcost + mincost[v]
        for u in range(V):
            if cost[u][v] == -1:
                continue
            mincost[u] = min(mincost[u], cost[v][u])
    return sumcost


n = int(raw_input())
A = [0] * n
for u in range(n):
    A[u] = map(int, raw_input().split())
 
result = prim(A)
print(result)

Python: #ALDS1_12_A Minimum Spanning Tree
import sys


n = int(input())
G = []
for i in range(n):
    input_list = list(map(int, sys.stdin.readline().strip().split()))
    adj = [j if j != -1 else float('inf') for j in input_list]
    adj[i] = 0
    G.append(adj)

p = ['unexplored'] * n  # 親を保存するリスト
d = [float('inf')] * n  # 距離を保存するリスト

p[0] = 0
d[0] = 0
u = 0

for _ in range(n):
    mincost = float('inf')
    for i in range(n):
        if (p[i] == 'unexplored') & (d[i] < mincost):
            mincost = d[i]
            u = i  # u is child

    for i in range(n):
        if (p[i] != 'unexplored') & (G[i][u] == mincost):
            p[u] = i
            break
            
    for i in range(n):
        if G[u][i] < d[i]:
            d[i] = G[u][i]
    # print(p)

ans = 0
for i in range(1, n):
    ans += G[p[i]][i]
print(ans)

Python: n=int(input())

ds=[i for i in range(n)]
def root(x):
  path_to_root = []
  while ds[x] != x:
    path_to_root.append(x)
    x = ds[x]
  for i in path_to_root:
    ds[i] = x
  return x
def same(x,y):
  return root(x) == root(y)
def unite(x,y):
  ds[root(x)] = root(y)

p=[] #[a,i,j]:i<j
for i in range(n):
  a=list(map(int,input().split()))
  for j in range(i+1,n):
    if a[j]!=-1: p.append([a[j],i,j])
p.sort(key=lambda x:x[0])
ans=0
for i in p:
  if same(i[1],i[2]): continue
  unite(i[1],i[2])
  ans+=i[0]
print(ans)

Python: INFTY = 1 << 21
WHITE = 0
GRAY = 1
BLACK = 2

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

d = [INFTY for i in range(n)]
p = [-1 for i in range(n)]
color = [WHITE 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())