Go: package main

import (
	"bufio"
	"fmt"
	"log"
	"math"
	"os"
	"strconv"
	"strings"
)

type color int

const (
	white color = iota // 未訪問
	mst                // MSTとして確定
)

// 頂点
type node struct {
	matrix   []int // 隣接行列
	minToMst int   // MSTへの重み最小値
	parent   int   // 最小値の相手
	color    color
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	n := eGetInt(scanner)

	nodes := make([]node, n)
	for i := 0; i < n; i++ {
		nodes[i].matrix = eAtoi((strings.Fields(eGetline(scanner))))
		nodes[i].parent = -1
		nodes[i].minToMst = math.MaxInt16
		nodes[i].color = white
	}

	// 初回はnode[0]がMSTに入るように,minToMstを設定
	nodes[0].minToMst = 0
	for { // 全部チェックするまで

		// どの頂点を新たにMSTに取り込むか
		min := math.MaxInt16
		u := -1
		for i := 0; i < n; i++ {
			if nodes[i].color == mst {
				continue
			}
			if nodes[i].minToMst < min {
				u = i
				min = nodes[i].minToMst
			}
		}

		if u == -1 {
			break
		}
		// MSTに追加する頂点決定
		nodes[u].color = mst

		// MSTに属していない頂点それぞれについて,MSTとの最小の重みを更新
		for i := 0; i < n; i++ {
			if nodes[i].color == mst {
				continue
			}
			if nodes[i].matrix[u] == -1 {
				// 接してない
				continue
			}
			if nodes[i].matrix[u] < nodes[i].minToMst {
				// node[u]との重みが最小
				nodes[i].minToMst = nodes[i].matrix[u]
				nodes[i].parent = u
			}
		}
	}

	sum := 0
	for _, v := range nodes {
		// node[0]はparentが入っていない
		if v.parent != -1 {
			sum += v.matrix[v.parent]
		}
	}
	fmt.Println(sum)
}

func eGetInt(scanner *bufio.Scanner) int {
	t := eAtoi(strings.Fields(eGetline(scanner)))
	return t[0]
}

func eGetline(p *bufio.Scanner) string {
	if !p.Scan() {
		if err := p.Err(); err != nil {
			log.Fatal(err.Error())
		}
		return ""
	}
	return p.Text()
}

func eAtoi(s []string) []int {
	ints := make([]int, len(s))
	var err error
	for i, e := range s {
		ints[i], err = strconv.Atoi(e)
		if err != nil {
			log.Fatal(err.Error())
		}
	}
	return ints
}

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];

// プリムのアルゴリズム（厳密解法)
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;
       // 最適点(コスト最小点)を探す
        for(int i=0;i<n;i++){
            if(minv > d[i] && color[i] != BLACK){
                u = i;
                minv = d[i];
            }
        }
        if(u == -1) break; // uに対しての辺がなかった場合
        color[u] = BLACK;
        
        // 次点の捜索
        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;
}

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;
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<queue>
#include<list>
#include<string>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#include<cmath>
using namespace std;

const int NIL = -1;
const int MAX = 20001;

int G[101][101];
int color[101], d[101], p[101];

int main(void)
{
	int n, m, mincost, u, min = 0;
	cin >> n;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			cin >> m;
			if (m == -1)
				G[i][j] = MAX;
			else
				G[i][j] = m;
		}
	}
	for (int i = 0; i < n; i++) {
		color[i] = 0;
		d[i] = MAX;
	}
	d[0] = 0;
	p[0] = -1;
	while (1) {
		mincost = MAX;
		for (int i = 0; i < n; i++) {
			if (color[i] != 2 && d[i] < mincost) {
				mincost = d[i];
				u = i;
			}
		}
		if (mincost == MAX)
			break;
		min += mincost;
		color[u] = 2;
		for (int v = 0; v < n; v++) {
			if (color[v] != 2) {
				if (G[u][v] < d[v]) {
					d[v] = G[u][v];
					p[v] = u;
					color[v] = 1;
				}
			}
		}
	}
	cout << min << endl;
	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vs = vector<string>;
using msi = map<string, int>;
using mii = map<int, int>;
using psi = pair<string, int>;
using pii = pair<int, int>;
using vlai = valarray<int>;
#define rep(i,n) for(int i=0;i<n;i++)
#define range(i,s,n) for(int i=s;i<n;i++)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define fs first
#define sc second
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define INF 1E9
#define EPS 1E-9
#define MOD (ll)(1E9+7)
#define PI 3.1415926535897932384

template <class T>ostream &operator<<(std::ostream &o, const vector<T> &v)
{
	rep(i, v.size()) {
		o << (i > 0 ? " " : "") << v[i];
	}
	return o;
}

int n;
vvi cost;
vi mincos;
vector<bool> used;

int prim() {
	rep(i, n) {
		mincos[i] = INF;
		used[i] = false;
	}
	mincos[0] = 0;
	int res = 0;
	while (1) {
		int v = -1;
		rep(u, n) {
			if(!used[u]&&(v==-1||mincos[u]<mincos[v])){
				v = u;
			}
		}
		if (v == -1) break;
		used[v] = true;
		res += mincos[v];

		rep(u, n) {
			mincos[u] = min(mincos[u], cost[v][u]);
		}
	}
	return res;
}

int main() {
	int a,b;
	cin >> n ;
	cost.resize(n);
	mincos.resize(n);
	used.resize(n);
	for (auto &i : cost) {
		i.resize(n);
	}
	rep(i, n) {
		rep(j, n) {
			cin >> cost[i][j];
			if (cost[i][j] == -1) cost[i][j] = INF;
		}
	}
	cout << prim() << endl;
}

C++: #include <bits/stdc++.h>
#define r(i,a,n) for(int i=a;i<n;i++)
using namespace std;
int main(){
	int n,p;
	while(cin>>n>>p,n){
		int q,a[10000][1261],ch[10000][1261],b,c,d,e;
		r(i,0,p)r(j,0,1261)ch[i][j]=a[i][j]=0;
		cin>>q;
		r(i,0,q){
			cin>>b>>c>>d>>e;
			if(e==1){a[d-1][b]++;ch[d-1][b]=c;}
			else{
				for(int j=b-1;;j--){
					if(ch[d-1][j]==c)break;
					a[d-1][j]++;
				}
			}
		}
		cin>>q;
		while(q--){
			int s=0;
			cin>>b>>c>>d;
			r(i,b,c)if(a[d-1][i])s++;
			cout<<s<<endl;
		}
	}
}