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())

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


def prim_mst(vn):
    isVisited = [False] * vn
    d = [0] + [2001] * (vn - 1)
    p = [-1] * vn

    while True:
        mincost = 2001
        for i in range(vn):
            if (not isVisited[i]) and (d[i] < mincost):
                mincost = d[i]
                u = i

        if mincost == 2001:
            break

        isVisited[u] = True

        for v in range(vn):
            if (not isVisited[v]) and (adj[u][v] != -1):
                if adj[u][v] < d[v]:
                    d[v] = adj[u][v]
                    p[v] = u

    print(sum(d))


prim_mst(n)

Python: from __future__ import division, print_function
from sys import stdin, maxint
 
 
def main():
    num = int(stdin.readline())
 
    M = []
    for _ in xrange(num):
        M.append([int(s) for s in stdin.readline().split()])
 
    g = set(xrange(1, num+1))
    index = g.pop()
    h = {index}
    weight = 0
 
    while g:
        minimum = maxint
        for j in h:
            mj = M[j-1]
            for i in g:
                if 0 <= mj[i-1] < minimum:
                    index = i
                    minimum = mj[i-1]
        h.add(index)
        g.remove(index)
        weight += minimum
 
    print(weight)
 
 
main()

Python: import sys
from collections import defaultdict

def push_vertex(vtx: int,queue: list, weights: dict, done: dict):
    queue.extend(weights[vtx])
    done[vtx] = True
    [queue.remove(x) for x in queue[:] if done[x[0]]]
    del weights[vtx]
    queue.sort(key=lambda x: x[1], reverse=True)
    return


def main():
    n = int(input())
    weights = defaultdict(list)
    for i in range(n):
        for idx, weight in enumerate(input().split()):
            if weight != '-1':
                weights[i+1].append((idx+1, int(weight)))
    done = {}
    for i in weights.keys():
        done[i] = False
    mst_weights = 0
    queue = []
    vtx = [*weights][0]
    push_vertex(vtx, queue, weights, done)

    while len(weights) != 0:
        new_vtx, new_vtx_weight = queue.pop()
        mst_weights += new_vtx_weight
        #print(f"connect to {new_vtx} ,weight={new_vtx_weight}")
        push_vertex(new_vtx, queue, weights, done)

    print(mst_weights)
    return

main()

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()