Go: package main

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

// Define disjoint-set forests

type vertexNo int

type vertex struct {
	number vertexNo
	rank int
	parent *vertex
}

func makeSet(number vertexNo) vertex {
	return vertex {
		number: number,
		rank: 0,
		parent: nil,
	}
}

func union(x, y *vertex) *vertex {
	return link(findSet(x), findSet(y))
}

func link(x, y *vertex) *vertex {
	if x.rank > y.rank {
		y.parent = x
		return x
	} else {
		x.parent = y
		if x.rank == y.rank {
			y.rank += 1
		}
		return y
	}
}

func findSet(v *vertex) *vertex {
	if v.parent == nil {
		return v
	}
	v.parent = findSet(v.parent)
	return v.parent
}

// Function to calculate minimum spanning tree

type matrix [][]int

type edge struct {
	one vertexNo
	two vertexNo
	weight int
}

const(
	MAX_VERTICES = 100
)

func newEdgesFromMatrix(matrix matrix) []edge {
	edges := make([]edge, 0, MAX_VERTICES * MAX_VERTICES)

	for i := 0; i < len(matrix); i++ {
		row := matrix[i]
		for j := i; j < len(row); j++ {
			if row[j] >= 0 {
				edge := edge{one: vertexNo(i+1), two: vertexNo(j+1), weight: row[j]}
				edges = append(edges, edge)
			}
		}
	}

	return edges
}

func solve(matrix matrix) int {
	nVertices := len(matrix)

	// initialize vertices
	vertices := make([]vertex, nVertices)
	for i := 0; i < nVertices; i++ {
		vertices[i] = makeSet(vertexNo(i+1))
	}

	// prepare edges sorted in the ascending order of weight
	edges := newEdgesFromMatrix(matrix)
	sort.Slice(edges, func(i, j int) bool {
		return edges[i].weight < edges[j].weight
	})

	unionCount := 0
	weightSum := 0
	for unionCount < nVertices-1 {
		for i := 0; i < len(edges); i++ {
			edge := edges[i]
			v1 := &vertices[edge.one-1]
			v2 := &vertices[edge.two-1]
			rep1 := findSet(v1)
			rep2 := findSet(v2)
			if rep1.number == rep2.number {
				continue
			}
			union(rep1, rep2)
			edges = append(edges[0:i], edges[i+1:]...)
			weightSum += edge.weight
			unionCount++
			break
		}
	}

	return weightSum
}

// main

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

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

	matrix := parseMatrix(n, sc)

	edges := newEdgesFromMatrix(matrix)
	sort.Slice(edges, func(i, j int) bool {
		return edges[i].weight < edges[j].weight
	})

	fmt.Println(solve(matrix))
}

func parseMatrix(n int, sc *bufio.Scanner) [][]int {
	matrix := make([][]int, n)
	for i := 0; i < n; i++ {
		matrix[i] = make([]int, n)
		for j := 0; j < n; j++ {
			x, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			matrix[i][j] = x
		}
	}
	return matrix
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

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

Python: n = int(input())
edgeList = []
rootList = [-1 for i in range(n)]

def getRoot(x):
    r = rootList[x]
    if r < 0:
        rootList[x] = x
    elif r != x:
        rootList[x] = getRoot(r)
    return rootList[x]
        
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)])
sumLength = 0
edgeList.sort(key=lambda x: x[0])
for e in edgeList:
    x = e[1]
    y = e[2]
    if x != y:
        sumLength += e[0]
        rootList[x] = rootList[y] = min(x, y)
print(sumLength)

Python: # coding: utf-8

class UnionFind:
    def __init__(self,N):
        self.par = [i for i in range(N)]
        self.rank = [1]*N
        
    def find(self, x):
        if self.par[x] == x:
            return x
        else:
            self.par[x] = self.find(self.par[x])
            return self.par[x]
    
    def unite(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        
        if self.rank[x] < self.rank[y]:
            self.par[x] = y
        else:
            self.par[y] = x
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1

    def same(self, x, y):
        return self.find(x) == self.find(y)
        
class Edge:
    def __init__(self, u, v, cost):
        self.u = u
        self.v = v
        self.cost = cost

def kruskal():
    es.sort(key=lambda x: x.cost)
    uf = UnionFind(V)
    res = 0
    for i in range(E):
        if not uf.same(es[i].u, es[i].v):
            uf.unite(es[i].u, es[i].v)
            res += es[i].cost
            
    return res

V = int(input().rstrip())
E = 0
es = []
for i in range(V):
    line = list(map(int, input().rstrip().split()))
    for j in range(V):
        if line[j] != -1:
            es.append(Edge(i,j,line[j]))
            E += 1

ans = kruskal()
print(ans)

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):
        for j in range(n):
            src = input()
            dst = src.replace('-1', 'INF')
            ai = list(map(int, dst.split()))
            A.append(ai)
    print(prim(A))

Python: N = int(input())
color = ["w" for _ in range(N)]
d = [float("inf") for _ in range(N)]
p = [-1 for _ in range(N)]

# Make M
M = [list(map(int, input().split())) for _ in range(N)]

d[0] = 0
while True:
    mincost = float("inf")
    for i in range(N):
        if color[i] != "b" and d[i] < mincost:
            mincost = d[i]
            u = i
    
    if mincost == float("inf"):
        break
    color[u] = "b"

    for v in range(N):
        if color[v] != "b" 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(1, N):
    s += M[i][p[i]]
print(s)

Python: from __future__ import division, print_function
from sys import stdin, maxint
 
 
def main():
    num = int(stdin.readline())
 
    y = []
    for _ in xrange(num):
        it = iter(int(s) for s in stdin.readline().split()[1:])
        y.append([(next(it), next(it)) for _ in xrange(next(it))])
    weight = [maxint] * num
    weight[0] = 0
    t = set(xrange(1, num))
    index = 0
 
    while t:
        for v, cost in y[index]:
            if v not in t:
                continue
            weight[v] = min(weight[v], cost + weight[index])
        index = min(t, key=lambda i: weight[i])
        t.remove(index)
    for i, d in enumerate(weight):
        print(i, d)
 
 
main()

Python: from __future__ import division, print_function
from sys import stdin, maxint
 
 
def main():
    num = int(stdin.readline())
 
    y = []
    for _ in xrange(num):
        it = iter(int(s) for s in stdin.readline().split()[1:])
        y.append([(next(it), next(it)) for _ in xrange(next(it))])
 
    weight = [maxint] * num
    weight[0] = 0
    t = set(xrange(1, num))
    index = 0
 
    while t:
        for v, cost in y[index]:
            if v not in t:
                continue
            weight[v] = min(weight[v], cost + weight[index])
 
        index = min(t, key=lambda i: weight[i])
        t.remove(index)
 
    for i, d in enumerate(weight):
        print(i, d)
 
 
main()

Python: def main():

    N = 100

    n = int(input())
    adj = [[0 for i in range(n)] for j in range(n)]

    for i in range(n):
        tmp = list(map(int, input().split()))
        u = tmp[0]
        u = u -1
        k = tmp[1]
        v = tmp[2:]
        for j in range(k):
            adj[u][v[j]-1] = 1

    for i in range(n):
        for j in range(n):
            print(adj[i][j], end=" ")
        print()

if __name__ == "__main__":
    main()