Go: package main

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

const (
	WHITE int = iota
	GRAY
	BLACK
)

type graph struct {
	G [][]int
	C []int
	D []int
	P []int
}

var INFTY = 1 << 32

func constructGraph() *graph {
	sc := bufio.NewScanner(os.Stdin)
	sc.Scan()
	n, _ := strconv.Atoi(sc.Text())

	g := make([][]int, n)
	c := make([]int, n)
	d := make([]int, n)
	p := make([]int, n)

	for i := 0; i < n; i++ {
		sc.Scan()
		fields := strings.Fields(sc.Text())
		g[i] = toIntSlice(fields)
	}

	return &graph{g, c, d, p}
}

func (g *graph) initMst() {
	for i := 0; i < len(g.G); i++ {
		g.C[i] = WHITE
		g.D[i] = INFTY
	}
	g.D[0] = 0
	g.P[0] = -1
}

func (g *graph) primMst() int {
	g.initMst()

	var u int
	for {
		mincost := INFTY
		for i := 0; i < len(g.G); i++ {
			if g.C[i] != BLACK && g.D[i] < mincost {
				mincost = g.D[i]
				u = i
			}
		}

		if mincost == INFTY {
			break
		}

		g.C[u] = BLACK

		for i := 0; i < len(g.G); i++ {
			if g.C[i] != BLACK && g.existEdge(u, i) {
				if g.G[u][i] < g.D[i] {
					g.D[i] = g.G[u][i]
					g.P[i] = u
				}
			}
		}
	}

	totalCost := 0
	for _, cost := range g.D {
		totalCost += cost
	}
	return totalCost
}

func (g *graph) existEdge(u, v int) bool {
	return g.G[u][v] != INFTY && g.G[v][u] != INFTY
}

func toIntSlice(s []string) []int {
	a := make([]int, len(s))
	for i, v := range s {
		num, _ := strconv.Atoi(v)
		if num == -1 {
			num = INFTY
		}
		a[i] = num
	}
	return a
}

func main() {
	g := constructGraph()
	fmt.Println(g.primMst())
}

Python: import sys
from collections import deque

sys.setrecursionlimit(1000000)
n = int(input())
graph = [[] for _ in range(n)]

global visited 
visited = [0 for _ in range(n)]
global Q, S, T

S = [0] #訪れた順
T = []
visited[0] = 1 #開始位置はすでに訪れたことにする

def input_graph(n):
  for i in range(n):
    vs = list(map(int, input().split()))
    graph[i] = vs
    """for j in range(n):
      if vs[j] != -1:
        tree[i].append([j, vs[j]])"""

def prim():
  global S
  cost = 0
  while len(S) < n:
    max_e = 3000
    ad_v = 0
    ad_list = []
    for s in S:
      for j in range(n):
        if graph[s][j] != -1 and j not in S:
          ad_list.append(graph[s][j])
          #print("s: ",s, " j: ",j, graph[s][j])
          if max_e > graph[s][j]:
            max_e = graph[s][j]
            ad_v = j
    S.append(ad_v)
    cost += max_e
  print(cost)
  

if __name__ == "__main__":
  input_graph(n)
  prim()

Python: import heapq
n = int(input())
ans = 0
cost = []
for i in range(n):
    L = list(map(int,input().split()))
    cost.append(L)
used = [False]*n
used[0] = True #島0から探索を始める。
edge = []
for i in range(n):
    T = []
    edge.append(T)
for i in range(n):
    for j in range(n):
        if cost[i][j] != -1:
            edge[i].append([cost[i][j],j])
P = edge[0]
P.sort()
while len(P) != 0:
    cur = heapq.heappop(P)
    d = cur[0]
    next = cur[1]
    if used[next] == True:
        continue
    used[next] = True
    ans += d
    for e in edge[next]:
        heapq.heappush(P,[e[0],e[1]])
print(ans)

Python: import heapq


class MinimumSpanningTree:
    """ Prim's algorithm: find minimum spanning tree
        Complexity: O(E log(V))
        used in GRL2A(AOJ)
    """

    def __init__(self, V, E, start=0, INF=10**9):
        """ V: the number of vertexes
            E: adjacency list (undirected graph)
            start: start vertex
            INF: Infinity cost
        """
        self.prim(V, E, start, INF)

    def prim(self, V, E, start=0, INF=10**9):
        used = [False] * V
        self.mincost = 0
        que = []
        heapq.heappush(que, (0, 0))
        while len(que) > 0:
            cost, v = heapq.heappop(que)
            if used[v]:
                continue
            used[v] = True
            self.mincost += cost
            for to, c in E[v]:
                heapq.heappush(que, (c, to))

    def minCost(self):
        return self.mincost

V = int(input())
edge = [[] for _ in range(V)]
for i in range(V):
    for j, d in enumerate(map(int, input().split())):
        if d != -1:
            edge[i].append((j, d))
mst = MinimumSpanningTree(V, edge)
print(mst.minCost())

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

for _ in range(n):
    tmp = [int(x) for x in input().split()]
    m.append(tmp)

edge_list = [] 

j = 1
for i in range(n-1):
    for k,x in enumerate(m[i][j:]):
        if x != -1:
            edge_list.append((x,i,k))
        else:
            pass
    j += 1
edge_list.sort()

root_list = [i for i in range(n)]

def root(x):
    path_to_root = []
    while root_list[x] != x:
        path_to_root.append(x)
        x = root_list[x]
    for node in path_to_root:
        root_list[node] = x
    return x

def is_same_root(x,y):
    return root(x) == root(y)

def unite(x,y):
    root_list[root(x)] = root(y)

cost = 0
for x in edge_list:
    w,p,q = x
    if is_same_root(p,q):
        pass
    else:
        cost += w
        unite(p,q)

print(cost)

Python: n = int(input())

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

ans = 0
mincost = [2001] * n
flag = [0] * n
mincost[0] = 0

while 1:
    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 a[v][j] == -1:
            continue
        mincost[j] = min(mincost[j], a[v][j])
print(ans)

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: def prim(n):
    d[0] = 0
    while True:
        cost_min = 10**9
        u = -1
        for i in range(n):
            weight = d[i]
            if flag_list[i] < 2 and weight < cost_min:
                u = i
                cost_min = weight
        if u == -1:
            break
        flag_list[u] = 2
        for v in range(n):
            edge = m[u][v]
            if flag_list[v] < 2 and edge > -1:
                if d[v] > edge:
                    d[v] = edge
                    p[v] = u
                    flag_list[v] = 1
    cnt = 0
    for i in range(n):
        if p[i] != -1:
            cnt += m[i][p[i]]
    return cnt


if __name__ == "__main__":
    n = int(input())
    m = []
    for _ in range(n):
        in_list = list(map(int, input().split()))
        m.append(in_list)

    flag_list = [0]*n # 0: 未到達, 1: 処理中, 2: 完了
    d = [10**9]*n
    p = [-1]*n
    print(prim(n))

Python: def kruskal(n):
    cost = []
    tree = [{i} for i in range(n)]
    while edge:
        cmin = min(weight)
        index = weight.index(cmin)
        i, j = edge[index]
        del weight[index], edge[index]
        for t in tree:
            if {i, j} <= t:
                break
        else:
            cost.append(cmin)
            for n in range(len(tree)):
                if i in tree[n]:
                    tmp = tree[n]
                    del tree[n]
                    break
            for n in range(len(tree)):
                if j in tree[n]:
                    tree[n] |= tmp
                    break
    return sum(cost)

n = int(input())
edge = []
weight = []
for i in range(n):
    for j, c in enumerate(map(int, input().split())):
        if c != -1 and not {i, j} in weight:
            edge.append({i, j})
            weight.append(c)
print(kruskal(n))