Go: package main

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

const BIG_COST = 3000

const (
	ST_NOT_YET = iota
	ST_JOINED
)

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

	nNodes := scanInt(sc)
	costs := make([][]int, nNodes)

	for r := 0; r < nNodes; r++ {
		costs[r] = make([]int, nNodes)
		for c := 0; c < nNodes; c++ {
			costs[r][c] = scanInt(sc)
		}
	}

	states := make([]int, nNodes)
	minCosts := make([]int, nNodes)

	for i := 1; i < nNodes; i++ {
		minCosts[i] = BIG_COST
	}

	for {
		var u int
		minCost := BIG_COST

		for i := 0; i < nNodes; i++ {
			if states[i] != ST_JOINED && minCosts[i] < minCost {
				minCost = minCosts[i]
				u = i
			}
		}

		// 全てのノードが MST に JOIN できたので終了。
		if minCost == BIG_COST {
			break
		}

		states[u] = ST_JOINED

		for v := 0; v < nNodes; v++ {
			cost := costs[u][v]

			// MST内の u と MST外の v との辺の重みをそれぞれ minCosts[v] として
			// 保存しておく。このうち辺の重みが最小となる v が次のループで MST に JOIN する。
			if states[v] != ST_JOINED && cost != -1 && cost < minCosts[v] {
				minCosts[v] = cost
			}
		}
	}

	sum := 0
	for _, cost := range minCosts {
		sum += cost
	}
	fmt.Println(sum)
}

func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

Python: n=int(input())
matrix=[list(map(int,input().split())) for _ in range(n)]
weight=[]
for x in range(n):
    for y in range(x,n):
        if matrix[x][y]>=0: weight.append((x,y,matrix[x][y]))
weight.sort(key=lambda x:x[2])
ans=0
p=[i for i in range(n)]

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)
        
for x,y,w in weight:
    if not is_same_set(x,y):
        unite(x,y)
        ans+=w
print(ans)

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], getRoot(i), getRoot(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: n = int(raw_input())
a = []

for i in range(n):
    inp = raw_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:
    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())
M=[list(map(int,input().split()))for _ in[0]*n]
d=[0]+[1e4]*n
b=[1]*n
a=0
while 1:
 u=-1
 for i in range(n):
  if b[i]and(u<0 or d[i]<d[u]):u=i
 if u<0:break
 b[u]=0
 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: def prim(n,M):
    d = [None]*n
    p = [None]*n
    searched = [0]*n
    
    for i in range(n):
        d[i] = float("inf")
        p[i] = -1
    
    d[0] = 0
    
    while True:
        minv = float("inf")
        u = -1
        for i in range(n):
            if minv > d[i] and not searched[i]:
                u = i
                minv = d[i]
        
        if u == -1:
            break
        searched[u] = 1
        for v in range(n):
            if (not searched[v]) and M[u][v] != -1:
                if d[v] > M[u][v]:
                    d[v] = M[u][v]
                    p[v] = u

    s = 0
    for i in range(n):
        if p[i] != -1:
            s += M[i][p[i]]
    return print(s)

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

Python: #!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys

WHITE, GRAY, BLACK = 0, 1, 2


def prim_span_tree():
    min_weight_vertices[0] = 0

    while True:
        min_cost = 2001
        current_vertex = -1
        for i in range(vertices_num):
            if color[i] != BLACK and min_weight_vertices[i] < min_cost:
                min_cost = min_weight_vertices[i]
                current_vertex = i

        if min_cost == 2001:
            break

        color[current_vertex] = BLACK

        for j in range(vertices_num):
            v_weight = int(init_vertices_matrix[current_vertex][j])
            if color[j] != BLACK and v_weight >= 0:
                if v_weight < min_weight_vertices[j]:
                    min_weight_vertices[j] = v_weight
                    parent_list[j] = current_vertex
                    color[j] = GRAY

    return min_weight_vertices


if __name__ == '__main__':
    _input = sys.stdin.readlines()
    vertices_num = int(_input[0])
    init_vertices_matrix = list(map(lambda x: x.split(), _input[1:]))

    parent_list, min_weight_vertices = [-1] * vertices_num, [2001] * vertices_num
    color = [WHITE] * vertices_num
    ans = prim_span_tree()
    print(sum(ans))

Python: 
def prim(cost):
    sumcost = 0
    V = len(cost)
    mincost = [float('inf')] * V
    used = [False] * V
    mincost[0] = 0
    while True:
        j = -1
        for i in range(V):
            if not used[i] and (j == -1 or mincost[i] < mincost[j]):
                j = i
        if j == -1:
            break
        used[j] = True
        sumcost = sumcost + mincost[j]
        for i in range(V):
            if cost[i][j] == -1:
                continue
            mincost[i] = min(mincost[i], cost[j][i])
    return sumcost

n = int(raw_input())
A = [0] * n
for i in range(n):
    A[i] = map(int, raw_input().split())

result = prim(A)
print(result)

Python: INFTY = 1 << 21
WHITE = 0
GRAY = 1
BLACK = 2
d = [INFTY for i in range(n)]
p = [-1 for i in range(n)]
color = [WHITE for i in range(n)]

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] = 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())

Python: def root(x):
    path = []
    while P[x] != x:
        path.append(x)
        x = P[x]
    for node in path:
        P[node] = x
    return x
def check(x,y):
    if root(x) == root(y):
        return 1
    else:
        return 0
def unite(x,y):
    P[root(x)] = root(y)        

n = int(input())
P = [i for i in range(n)]
omomi = []
for k in range(n):
    s = list(map(int,input().split()))
    for l in range(n):
        if s[l] != -1:
            omomi.append([s[l],k,l])
omomi.sort()
ans = 0
for yee in range(len(omomi)):
    if check(omomi[yee][1],omomi[yee][2]) == False:
            unite(omomi[yee][1],omomi[yee][2])
            ans+=omomi[yee][0]
print(ans)