Go: package main

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

func main() {
	r := bufio.NewReader(os.Stdin)

	var n int
	fmt.Fscan(r, &n)
	cs := make([]map[int]int, n) // []v_i -> c_i
	for h := 0; h < n; h++ {
		var u, k int
		fmt.Fscan(r, &u, &k)
		m := make(map[int]int)
		for i := 0; i < k; i++ {
			var v, c int
			fmt.Fscan(r, &v, &c)
			m[v] = c
		}

		cs[u] = m
	}

	q := make(map[int]int)
	q[0] = 0
	visited := make(map[int]struct{})
	out := make([]int, n)

	for len(q) > 0 {
		u := top(q)
		for uu, c := range cs[u] {
			// Consider the connection between u and uu.
			if _, ok := visited[uu]; ok {
				continue
			}
			if d, ok := q[uu]; !ok || d > q[u]+c {
				q[uu] = q[u] + c
			}
		}

		out[u] = q[u]
		delete(q, u)
		visited[u] = struct{}{}
	}

	for u, d := range out {
		fmt.Println(u, d)
	}
}

func top(q map[int]int) int {
	minu := -1
	min := -1
	for u, d := range q {
		if min < 0 || d < min {
			minu = u
			min = d
		}
	}

	return minu
}

C++: #include<bits/stdc++.h>
using namespace std;
#define rp(i,j) for(long long i=0;i<j;i++)
#define rep(i,j,k) for(long long i=j;i<k;i++)
#define mod 1000000007
#define NIL -1
#define MAX 100
static const int INFTY=(1<<21);
typedef long long ll;
int n,u;
int M[MAX][MAX];
int d[MAX];
int color[MAX];
void dijkstra(){
    rp(i,n){
        d[i]=INFTY;
        color[i]=0;
    }
    d[0]=0;
    color[0]=1;
    while(1){
        int minv=INFTY;
        rp(i,n){
            if(color[i]!=2&&d[i]<minv){
                minv=d[i];
                u=i;
            }
        }
        if(minv==INFTY)break;
        color[u]=2;
        rp(i,n){
            if(d[u]+M[u][i]<d[i]){
                d[i]=d[u]+M[u][i];
                color[i]=1;
            }
        }

    }
}
int main(){
    int u,k,v,c;
    cin>>n;
    rp(i,n){
        rp(j,n)M[i][j]=INFTY;
        cin>>u>>k;
        rp(j,k){
            cin>>v>>c;
            M[u][v]=c;
        }
    }
    dijkstra();
    rp(i,n)cout<<i<<" "<<d[i]<<endl;
}

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

int n;
vector<pair<int, int>> adj[100];
int *d;

void dijkstra() {
    priority_queue<pair<int, int>> PQ;
    int d[n], color[n];

    for (int i = 0; i < n; i++) {
        d[i] = INFTY;
        color[n] = WHITE;
    }
    d[0] = 0;
    PQ.push(make_pair(0, 0));

    while (!PQ.empty()) {
        pair<int, int> f = PQ.top();
        PQ.pop();

        int u = f.second;
        color[u] = BLACK;

        if (d[u] < f.first * (-1)) { continue; }

        for (int j = 0; j < adj[u].size(); j++) {
            int v = adj[u][j].first;
            if (color[v] == BLACK) { continue; }
            if (d[u] + adj[u][j].second < d[v]) {
                d[v] = d[u] + adj[u][j].second;
                // printf("d[%d] = %d\n", v, d[v]);
                PQ.push(make_pair(d[v] * (-1), v));
                color[v] = GRAY;
            }
        }
    }
    
    for (int i = 0; i < n; i++) {
        printf("%d %d\n", i, d[i]);
    }
}

int main() {
    scanf("%d", &n);

    // adj = new vector<pair<int, int>>[n];

    for (int i = 0; i < n; i++) {
        int u, k;
        scanf("%d %d", &u, &k);
        for (int j = 0; j < k; j++) {
            int v, c;
            scanf("%d %d", &v, &c);
            adj[u].push_back(make_pair(v, c));
        }
    }

    dijkstra();

    return 0;
}

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;
}