Go: package main

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

const (
	MAX_N      = 200
	MAX_WEIGHT = 2000
)

type Edge struct {
	start  int
	end    int
	weight int
}

type ShortestInfo struct {
	edges    []Edge
	shortest int
}

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

	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}

	shortestList := make([]ShortestInfo, n)
	for i := 1; i < n; i++ {
		shortestList[i] = ShortestInfo{edges: []Edge{}, shortest: MAX_N*MAX_WEIGHT + 1}
	}

	adjacentMatrix := make([][]int, n)
	for i := 0; i < n; i++ {
		adjacentMatrix[i] = make([]int, n)
		for j := 0; j < n; j++ {
			v, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			adjacentMatrix[i][j] = v
		}
	}

	mst([]int{1}, shortestList, adjacentMatrix)
	fmt.Println(calculateMinWeight(shortestList))
}

func calculateMinWeight(shortestList []ShortestInfo) int {
	visitedList := make([]bool, len(shortestList))
	visitedList[0] = true
	sumWeight := 0
	for !visitedAll(visitedList) {
		shortestInfo := shortestList[0]
		shortestList = shortestList[1:]
		edges := shortestInfo.edges
		for _, edge := range edges {
			if !visitedList[edge.end-1] {
				visitedList[edge.end-1] = true
				sumWeight += edge.weight
			}
		}
	}
	return sumWeight
}

func visitedAll(visitedList []bool) bool {
	for _, v := range visitedList {
		if !v {
			return false
		}
	}
	return true
}

func mst(nodeStack []int, shortestList []ShortestInfo, adjacentMatrix [][]int) {
	for len(nodeStack) > 0 {
		currentNode := nodeStack[0]
		nodeStack = nodeStack[1:]
		currentShortest := getShortest(currentNode, shortestList)
		adjacents := findAdjacents(currentNode, adjacentMatrix)
		for i := 0; i < len(adjacents); i++ {
			adj := adjacents[i]
			s := getShortest(adj.end, shortestList)
			if currentShortest.shortest+adj.weight < s.shortest || (currentShortest.shortest+adj.weight == s.shortest && len(currentShortest.edges)+1 > len(s.edges)) {
				setShortest(adj.end, adj, currentShortest, shortestList)
				nodeStack = append(nodeStack, adj.end)
			}
		}
	}
}

func getShortest(node int, shortestList []ShortestInfo) ShortestInfo {
	return shortestList[node-1]
}

func setShortest(node int, edge Edge, currentShortest ShortestInfo, shortestList []ShortestInfo) {
	newEdges := make([]Edge, len(currentShortest.edges)+1)
	for i := 0; i < len(newEdges)-1; i++ {
		newEdges[i] = currentShortest.edges[i]
	}
	newEdges[len(newEdges)-1] = edge
	shortestInfo := ShortestInfo{edges: newEdges, shortest: currentShortest.shortest + edge.weight}
	shortestList[node-1] = shortestInfo
}

func findAdjacents(currentNode int, adjacentMatrix [][]int) []Edge {
	adjacents := adjacentMatrix[currentNode-1]
	edges := []Edge{}
	for i, v := range adjacents {
		if v > 0 {
			edges = append(edges, Edge{start: currentNode, end: i + 1, weight: v})
		}
	}
	return edges
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

Python: n = int(input())
M = [list(map(int, input().split())) for _ in range(n)]
INF = 100000000000
color = ['White']*n
d = [INF]*n
p = [-1]*n
d[0] = 0
sum = 0

while True:
    minct = INF
    u = -1
    for i in range(n):
        if color[i] != 'Black' and d[i] < minct:
            minct = d[i]
            u = i
    if minct == INF:
        break
    color[u] = 'Black'
    for j in range(n):
        if color[j] != 'Black' and M[u][j] != -1:
            if M[u][j] < d[j]:
                d[j] = M[u][j]
                p[j] = u
                color[j] = 'Gray'
for k in range(n):
    if p[k] != -1:
        sum += M[k][p[k]]
print(sum)

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()