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: MAX = 100
INF = 1 << 21
WHITE = 0 # ?????¢?´¢
GRAY = 1  # ??¢?´¢????±?
BLACK = 2 # ??¢?´¢??????

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

for i in range(n):
    for j in range(n):
        if M[i][j] == -1:
            M[i][j] = INF

d = [INF for i in range(n)] # ??¢?´¢????±?
p = [-1 for i in range(n)]  # ??????????????????
color = [WHITE for i in range(n)]

def prim():
    global M, d, p, color

    d[0] = 0

    while(1):
        minv, u = INF, -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] != INF:
                if d[v] > M[u][v]:
                    d[v], p[v], color[v] = M[u][v], u, GRAY
    return sum([M[i][p[i]] for i in range(n) if p[i] != -1])


print(prim())

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: N = int(input())
P = [i for i in range(N)]
weight = []

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

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

def unite(x,y):
    P[root(x)] = root(y)
    
# まずは辺の重さをソートするために辺の重さの配列を作りましょう→マイナス1は除外
for i in range(N):
    lis = list(map(int,input().split()))
    for j in range(N):
        if lis[j] == -1:
            continue
        else:
            weight.append([lis[j],i,j])
# ソートされた順に小さい順から次々とuniteして行こう
weight.sort()
length = len(weight)
k = 0
total_weight = 0

for k in range(length):
    if is_same_set(weight[k][1],weight[k][2]):
        continue
    else:
        unite(weight[k][1],weight[k][2])
        total_weight += weight[k][0]

print(total_weight)
    
# その際にもし付け加えてis_same_set(x,y)がtrueだったらやめよう

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

for i in range(n):

    line = list(map(int, input().split()))

    for i in range(len(line)):
        if line[i] == -1:
            line[i] = infinity
    a.append(line)

checked = [False] * n
d = [infinity] * n
checked[0] = True
ansswer = 0
next = 0

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

    minimumNeightbor = 0
    minimumWeight = infinity

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

    checked[minimumNeightbor] = True
    next = minimumNeightbor
    ansswer += minimumWeight

print(ansswer)

Python: INF = float("inf")
def MAIN():
    n = int(input())
    M = [[INF] * 101 for _ in range(101)]
    for i in range(n):
        for j, e in enumerate(map(int, input().split())):
            if e != -1:
                M[i][j] = e
    def prim():
        d = [INF] * n
        t = [-1] * n
        color = [0] * n
        d[0] = 0
        while True:
            minv = INF
            u = -1
            for i in range(n):
                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 d[v] > M[u][v]:
                    d[v] = M[u][v]
                    t[v] = u
                    color[v] = 1
        return sum(d)
    print(prim())
MAIN()

Python: # minimum_spanning_tree
def prim(adj_matrix, n):
    dist = [float("inf") for _ in range(n)]  # 訪問確定したノードからの最短距離
    visited = [False for _ in range(n)]  # ノードの訪問が確定したか
    parent = [-1 for _ in range(n)]  # start -> endを保存するためのstart？
    cost = 0
    inf = float("inf")

    start = 0
    visited[start] = True
    dist[start] = 0
    while True:
        # startから直接つながっている未訪問ノードをもとに、距離の最小値を更新する
        for end in range(n):
            if not visited[end] and adj_matrix[start][end] > -1 and adj_matrix[start][end] < dist[end]:
                dist[end] = adj_matrix[start][end]
                parent[end] = start

        min_cost = inf
        for nextnode in range(n):
            # dist_nodeの中から最もコストの短いノードを探す。そのノードは訪問確定。それを次回のstartとする。
            if not visited[nextnode] and dist[nextnode] < min_cost:
                min_cost = dist[nextnode]
                start = nextnode
        if min_cost == inf:
            break

        visited[start] = True
        cost += min_cost

    return parent, cost


def main():
    n = int(input())
    adj_matrix = []
    for _ in range(n):
        row = input().split()
        adj_matrix.append(list(map(int, row)))
    parent, cost = prim(adj_matrix, n)
    print(cost)


if __name__ == "__main__":
    main()

Python: n = int(input())
M = [[float("inf") for i in range(n)] for i in range(n)]
for i in range(n):
 L = list(map(int, input().split()))
 for j,v in enumerate(L):
  if v != -1:
   M[i][j] = v

def prim():
 color = [0] * n
 d = [float("inf")] * n
 p = [-1] * n
 d[0] = 0

 while True:
  minv = float("inf")
  u = -1
  for i in range(n):
   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] != float("inf"):
    if d[v] > M[u][v]:
     d[v] = M[u][v]
     p[v] = u
     color[v] = 1
 sum = 0
 for i in range(n):
  if p[i] != -1:
   sum += M[i][p[i]]
 return str(sum)

print(prim())

Python: def prim():
    global n
    global ct
    color=[0]*n
    d=[float('inf')]*n
    d[0]=0
    while True:
        mincost=float('inf')
        for i in xrange(n):
            if color[i]!=2 and d[i]<mincost:
                mincost=d[i]
                u=i
        if mincost==float('inf'):
            break
        ct+=d[u]
        color[u]=2
        for v in xrange(n):
            if color[v]!=2 and m[u][v]!=-1:
                if m[u][v]<d[v]:
                    d[v]=m[u][v]
                    color[v]=1
    
if __name__=='__main__':
    n=input()
    m=[map(int,raw_input().split()) for _ in xrange(n)]
    ct=0
    prim()
    print(ct)