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: import heapq


class MinimumSpanningTree:
    """ Prim's algorithm: find minimum spanning tree
        Complexity: O(E log(V))
        used in GRL2A(AOJ)
    """

    def __init__(self, V, E, start=0, INF=10**9):
        """ V: the number of vertexes
            E: adjacency list (undirected graph)
            start: start vertex
            INF: Infinity cost
        """
        self.prim(V, E, start, INF)

    def prim(self, V, E, start=0, INF=10**9):
        used = [False] * V
        self.mincost = 0
        que = []
        heapq.heappush(que, (0, 0))
        while len(que) > 0:
            cost, v = heapq.heappop(que)
            if used[v]:
                continue
            used[v] = True
            self.mincost += cost
            for to, c in E[v]:
                heapq.heappush(que, (c, to))

    def minCost(self):
        return self.mincost

V = int(input())
edge = [[] for _ in range(V)]
for i in range(V):
    for j, d in enumerate(map(int, input().split())):
        if d != -1:
            edge[i].append((j, d))
mst = MinimumSpanningTree(V, edge)
print(mst.minCost())

Python: n = int(input())
m = []

for _ in range(n):
    tmp = [int(x) for x in input().split()]
    m.append(tmp)

edge_list = [] 

j = 1
for i in range(n-1):
    for k,x in enumerate(m[i][j:]):
        if x != -1:
            edge_list.append((x,i,k))
        else:
            pass
    j += 1
edge_list.sort()

root_list = [i for i in range(n)]

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

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

def unite(x,y):
    root_list[root(x)] = root(y)

cost = 0
for x in edge_list:
    w,p,q = x
    if is_same_root(p,q):
        pass
    else:
        cost += w
        unite(p,q)

print(cost)

Python: n = int(input())

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

ans = 0
mincost = [2001] * n
flag = [0] * n
mincost[0] = 0

while 1:
    v = -1
    for j in range(n):
        if flag[j] != 1 and (v == -1 or mincost[j] < mincost[v]):
            v = j
    if v == -1:
        break
    flag[v] = 1
    ans += mincost[v]
    for j in range(n):
        if a[v][j] == -1:
            continue
        mincost[j] = min(mincost[j], a[v][j])
print(ans)

Python: import heapq
from collections import defaultdict
v_num = int(input())
edges = defaultdict(list)
for i in range(v_num):
    data = [int(n) for n in input().split(" ")[1:]]
    for j in range(i + 1, v_num):
        if data[j] != -1:
            edges[i].append([data[j], j])
            edges[j].append([data[j], i])
queue = []
heapq.heapify(queue)
for c in edges[0]:
    heapq.heappush(queue, c)
visited = {0}
answer = 0
while len(visited) < v_num:
    q = heapq.heappop(queue)
    weight, one = q[0], q[1]
    if one in visited:
        continue
    answer += weight
    for e in edges[one]:
        heapq.heappush(queue, e)
    visited |= {one}
print(answer)

Python: def prim(n):
    d[0] = 0
    while True:
        cost_min = 10**9
        u = -1
        for i in range(n):
            weight = d[i]
            if flag_list[i] < 2 and weight < cost_min:
                u = i
                cost_min = weight
        if u == -1:
            break
        flag_list[u] = 2
        for v in range(n):
            edge = m[u][v]
            if flag_list[v] < 2 and edge > -1:
                if d[v] > edge:
                    d[v] = edge
                    p[v] = u
                    flag_list[v] = 1
    cnt = 0
    for i in range(n):
        if p[i] != -1:
            cnt += m[i][p[i]]
    return cnt


if __name__ == "__main__":
    n = int(input())
    m = []
    for _ in range(n):
        in_list = list(map(int, input().split()))
        m.append(in_list)

    flag_list = [0]*n # 0: 未到達, 1: 処理中, 2: 完了
    d = [10**9]*n
    p = [-1]*n
    print(prim(n))

Python: def kruskal(n):
    cost = []
    tree = [{i} for i in range(n)]
    while edge:
        cmin = min(weight)
        index = weight.index(cmin)
        i, j = edge[index]
        del weight[index], edge[index]
        for t in tree:
            if {i, j} <= t:
                break
        else:
            cost.append(cmin)
            for n in range(len(tree)):
                if i in tree[n]:
                    tmp = tree[n]
                    del tree[n]
                    break
            for n in range(len(tree)):
                if j in tree[n]:
                    tree[n] |= tmp
                    break
    return sum(cost)

n = int(input())
edge = []
weight = []
for i in range(n):
    for j, c in enumerate(map(int, input().split())):
        if c != -1 and not {i, j} in weight:
            edge.append({i, j})
            weight.append(c)
print(kruskal(n))