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
	for len(edges) > 0 {
		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
	}
	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: INF = 9999


def prim(M):
    n = len(M)
    color = [0] * n
    d = [INF] * n
    d[0] = 0

    while True:
        minv = INF
        u = -1
        for i in range(n):
            # Black:2
            if minv > d[i] and color[i] != 2:
                u = i
                minv = d[i]
        if u == -1: break
        color[u] = 2

        for v in range(n):
            if color[v] != 2 and M[u][v] != INF:
                if d[v] > M[u][v]:
                    d[v] = M[u][v]
    return sum(d)


if __name__ == '__main__':
    n = int(input())
    A = []
    for i in range(n):
        src = input()
        dst = src.replace('-1', str(INF))
        ai = list(map(int, dst.split()))
        A.append(ai)
    print(prim(A))

Python: INFINITY = 10 ** 10
WHITE = 0
GRAY = 1
BLACK = 2


n = int(input())
M = [[INFINITY] * n for _ in range(n)]

for i in range(n):
    for j, weight in enumerate(map(int, input().split())):
        if weight == -1:
            weight = INFINITY

        M[i][j] = weight


def prim():
    color = [WHITE] * n
    d = [INFINITY] * n
    p = [None] * n

    d[0] = 0
    p[0] = -1

    while True:
        cost_min = INFINITY
        for i in range(n):
            if color[i] != BLACK and d[i] < cost_min:
                cost_min = d[i]
                top_now = i

        if cost_min == INFINITY:
            break
    
        color[top_now] = BLACK

        for v in range(n):
            if color[v] == BLACK or M[top_now][v] == INFINITY:
                continue

            if M[top_now][v] < d[v]:
                d[v] = M[top_now][v]
                p[v] = top_now
                color[v] = GRAY

    return sum(d)

cost_min = prim()
print(cost_min)

Python: def prim(n, M):
    color = [0 for _ in range(n)]
    d = [5000 for _ in range(n)]
    p = [-1 for _ in range(n)]

    d[0] = 0

    while True:
        mincost = 100000
        u = -1

        for i, dt in enumerate(d):
            if dt < mincost and color[i] != 1:
                mincost = dt
                u = i

        # ??´??°???????????£?????´???
        if mincost == 100000:
            break

        color[u] = 1

        for v in range(n):
            # ????????????, ?????????????¨???????????????¨??????
            if M[u][v] != 5000 and color[v] != 1:
                if M[u][v] < d[v]:
                    d[v] = M[u][v]
                    p[v] = u

    all_sum = 0

    for i, p_dt in enumerate(p):
        if p_dt != -1:
            all_sum += M[i][p_dt]

    return all_sum


def main():
    n = int(input())
    M = []

    for _ in range(n):
        dt = input().split(' ')
        M.append([5000 if int(d) == -1 else int(d) for d in dt])

    print(M)

    answer = prim(n, M)

    print(answer)

if __name__ == '__main__':
    main()

Python: v = int(input())
G= [[int(i) for i in input().split()] for i in range(v)]
        
def prim(G, v):
    Vn = set([1])
    En = set([])
    V = set(range(1, v+1))
    while Vn != V:
        m = float('inf')
        for u in Vn:
            for v in V - Vn:
                if G[u - 1][v - 1] == -1:continue
                if G[u - 1][v - 1] < m:
                    m = G[u - 1][v -1]
                    k = (u,v)
        Vn.add(k[1])
        En.add(k)
    return En

print(sum(G[u - 1][v -1] for u,v in prim(G, v)))

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())
    a = []

    for i in range(n):
        a.append([int(j) for j in input().split()])

    checked = [False] * n
    tree = [0]
    checked[0] = True
    ans = 0

    for i in range(n - 1):
        min_w = float('inf')

        for u in tree:
            for j in range(n):
                if a[u][j] != -1 and not checked[j]:
                    if min_w > a[u][j]:
                        min_w = a[u][j]
                        min_n = j

        checked[min_n] = True
        tree.append(min_n)
        ans += min_w

    print(ans)



if __name__ == '__main__':
    solve()

Python: # Minimum Spanning Tree

INF = 10**5
N, *W = map(int, open(0).read().split())
W = tuple(zip(*[iter(INF if w < 0 else w for w in W)]*N))

S = set([0])
ans = 0
while len(S) < N:
    min_w = INF
    u = -1
    for v in S:
        for j, w in enumerate(W[v]):
            if j not in S and w < min_w:
                min_w = w
                u = j

    ans += min_w
    S.add(u)
    
print(ans)

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

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

# ?????????O(n)????????£?????????
class union_find(object):
 	"""union-find tree"""
 	def __init__(self, length):
 		self.length = length
 		self.unionnumber=0
 		self.unionlist=[[]]
 		self.num=list(-1 for i in range(length))

 	def unite(self,i,j):
 		if self.num[i]==-1:
 			if self.num[j]==-1:
 				self.unionlist[self.unionnumber].extend([i,j])
 				self.num[i]=self.unionnumber
 				self.num[j]=self.unionnumber
 				self.unionnumber+=1
 				self.unionlist.append([])
 			else:
 				tmp=i 
 				i=j 
 				j=tmp 
 		if self.num[i]!=-1:
 			if self.num[j]!=-1:
 				if self.num[i]==self.num[j]:
 					pass
 				else:
 					self.unionlist[self.num[i]].extend(self.unionlist[self.num[j]])
 					tmp=self.num[j]
 					for k in self.unionlist[self.num[j]]:
 						self.num[k]=self.num[i]
 					self.unionlist[tmp]="del"
 			else:
 				self.num[j]=self.num[i]
 				self.unionlist[self.num[i]].append(j)

 	def same(self,i,j):
 		if self.num[i]==-1 or self.num[j]==-1:
 			return(False)
 		else:
 			return(self.num[i]==self.num[j])

# ?????????=-1
def Kruskal(matrix):
	length=len(matrix)
	edgelist=[]
	for i in range(length):
		for j in range(i+1):
			if matrix[i][j]!=-1:
				edgelist.append([j,i,matrix[i][j]])
	edgelist.sort(key=lambda x:x[2],reverse=True)
	result=[[-1 for i in range(length)] for j in range(length)]
	union=union_find(length)
	while(edgelist!=[]):
		edge=edgelist.pop()
		i,j,score=edge
		if union.same(i,j):
			pass
		else:
			union.unite(i,j)
			result[i][j]=score
			result[j][i]=score
		
	return(result)

a=Kruskal(matrix)
count=0
for i in range(len(a)):
	for j in range(i):
		if a[i][j]!=-1:
			count+=a[i][j]

print(count)