Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
type Node struct {
	cost int
	done bool
}

type Edge struct {
	to, cost int
}

const INF = 1 << 60

func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N := sc.nextInt()
	nodes := make([]Node, N)
	for i := 0; i < N; i++ {
		nodes[i].cost = INF
	}
	E := make([][]Edge, N)
	for i := 0; i < N; i++ {
		id, k := sc.nextInt(), sc.nextInt()
		for j := 0; j < k; j++ {
			to, cost := sc.nextInt(), sc.nextInt()
			E[id] = append(E[id], Edge{to, cost})
		}
	}
	nodes[0].cost = 0
	for {
		cur := 0
		minCost := INF
		for i := 0; i < N; i++ {
			n := nodes[i]
			if !n.done && n.cost < minCost {
				cur = i
				minCost = n.cost
			}
		}
		if minCost == INF {
			break
		}
		nodes[cur].done = true
		for i := 0; i < len(E[cur]); i++ {
			to, cost := E[cur][i].to, E[cur][i].cost+nodes[cur].cost
			if !nodes[to].done && cost < nodes[to].cost {
				nodes[to].cost = cost
			}
		}
	}

	for i := 0; i < N; i++ {
		fmt.Fprintln(wtr, i, nodes[i].cost)
	}
	wtr.Flush()
}

C++: #include<iostream>
#include<sstream>
#include<vector>
#include<climits>

using namespace std;

struct E
{
	int from, to;
	long cost;
};

int main(){
	ostringstream out;

	int n, u, k;
	cin >> n;

	vector<long> d(n);
	vector<E> e;

	fill(d.begin(),d.end(),LONG_MAX);
	d[0]=0;

	for(int i=0;i<n;i++){
		cin >> u >> k;
		for(int j=0;j<k;j++){
			E es={u,0,0};
			cin >> es.to >> es.cost; 
			e.push_back(es);
		}
	}

	while(true){
		bool update=false;
		for(int i=0;i<e.size();i++){
			if(d[e[i].from]!=LONG_MAX&&d[e[i].to]>d[e[i].from]+e[i].cost){
				d[e[i].to]=d[e[i].from]+e[i].cost;
				update=true;
			}
		}
		if(!update)break;
	}

	for(int i=0;i<n;i++)
		out << i << " " << d[i] << endl;

	cout << out.str();
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <climits>
using namespace std;

const int WHITE = 0;
const int GRAY = 1;
const int BLACK = 2;

int n;
vector<vector<int>> G;
vector<int> d;
vector<int> p;
vector<int> colors;

void sssp(int s){
    d[s] = 0;
    while(true){
        int cur_min = INT_MAX;
        int min_id = -1;
        for(int i =0;i<n;i++){
            if(colors[i]!=BLACK && d[i] < cur_min){
                min_id = i;
                //printf("%d %d\n",cur_min,d[i]);
                cur_min = d[i];
            }
        }
        if(min_id==-1) break;
        int u = min_id;
        colors[u] = BLACK;
        for(int v = 0;v<n;v++){
            if(colors[v] !=BLACK && G[u][v]!=INT_MAX){
                if(d[u]+G[u][v] < d[v]){
                    d[v] = d[u]+G[u][v];
                    p[v] = u;
                }
            }
        }
    }
    for(int i =0;i<n;i++) printf("%d %d\n",i,d[i]);
}

int main()
{
    //freopen("data.txt","r",stdin);
    cin >> n;
    G.resize(n,vector<int>(n,INT_MAX));
    d.resize(n,INT_MAX);
    p.resize(n,-1);
    colors.resize(n,WHITE);
    for(int i =0;i<n;i++){
        int u,k;
        cin >>u>>k;
        for(int j=0;j<k;j++){
            int v,c;
            cin >> v >>c;
            G[u][v] = c;
        }
    }
    sssp(0);
    //printf("YES\n");
    return 0;
}

C++: #include<iostream>
using namespace std;
#define MAX 108
#define black 2
#define gray 1
#define white 0
#define INFTY 1<<21
int mark[MAX][MAX];
int color[MAX];
int d[MAX];
int p[MAX];
int n;
inline void display(){
	cout<<endl;
	for(int i = 0;i<n;++i){
		for(int j = 0;j<n;++j)
			cout<<mark[i][j]<<' ';
	cout<<endl;
	}
	cout<<endl;
} 
void dijkstra( int begin ){
	for(int i = 0;i<n;++i){
		d[i] = INFTY;
		p[i] = -1;
		color[i] = white;
	}
	int mincost,u;
	d[0] = 0;
	
	while( true ){
		mincost = INFTY;
		for(int i= 0;i<n;++i)
			if(black!=color[i]&&d[i]<mincost){
				u = i;
				mincost = d[i];
			}
		if(INFTY==mincost)break;
		color[u] = black;
		for(int i =0;i<n;++i)
			if(black!=color[i]&&mark[u][i]!=-1&&d[i]>mincost+mark[u][i]){
				d[i] = mincost+mark[u][i];
				p[i] = u;
				color[i] = gray;
			}
	}
	for(int i = 0;i<n;++i)
		cout<<i<<' '<<d[i]<<endl;
} 

int main(){
	int u,k,vx,c;
	cin>>n;
	for(int i = 0;i<n;++i)
		for(int j=0;j<n;++j)
			mark[i][j] = -1;
	for(int i =0;i<n;++i){
		cin>>u>>k;
		for(int j = 0;j<k;++j){
			cin>>vx>>c;
			mark[u][vx] = c;
		}
	}
	
//	display();
	dijkstra(0);
	return 0;
}
/*
5
0 3 2 3 3 1 1 2
1 2 0 2 3 4
2 3 0 3 3 1 4 1
3 4 2 1 0 1 1 4 4 3
4 2 2 1 3 3


*/

C++: #include<iostream>
using namespace std;
static const int MAX =100;
static const int INFTY = (1<<21);
static const int WHITE = 0;
static const int GRAY =1;
static const int BLACK=2;

int n, M[MAX][MAX];

int prim(){
  int u,minv;
  int d[MAX],p[MAX],color[MAX];

  for(int i = 0;i<n;i++){
    d[i]=INFTY;
    p[i]=-1;
    color[i]=WHITE;
  }
  d[0]=0;

  while(1){
    minv=INFTY;
    u=-1;
    for(int i=0;i<n;i++){
      if(minv>d[i]&&color[i]!=BLACK){
      u=i;
      minv=d[i];
    }
  }
  if(u==-1)break;
  color[u]=BLACK;
  for(int v =0;v<n;v++){
    if(color[v]!=BLACK&& M[u][v]!=INFTY){
      if(d[v]>M[u][v]){
      d[v]=M[u][v];
      p[v]=u;
      color[v]=GRAY;
      }
    }
  }
  }
  int sum=0;
  for(int i=0;i<n;i++){
    if(p[i]!=-1) sum+=M[i][p[i]];
  }
  return sum;
}

int main(){
  cin >>n;

  for(int i=0;i<n;i++){
    for(int j=0;j<n;j++){
      int e; cin >>e;
      M[i][j] =(e==-1) ? INFTY : e;
    }
  }

  cout << prim() << endl;

  return 0;
}