Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

const INF = 0x7FFFFFFF

var pass [][]int

func main() {
	for scanner.Scan() {
		pass = make([][]int, 200)
		for i := range pass {
			pass[i] = make([]int, 200)
		}
		buf := strings.Split(scanner.Text(), " ")
		c, _ := strconv.Atoi(buf[0])
		n, _ := strconv.Atoi(buf[1])
		m, _ := strconv.Atoi(buf[2])
		s, _ := strconv.Atoi(buf[3])
		d, _ := strconv.Atoi(buf[4])
		if c == 0 && n == 0 && m == 0 && s == 0 && d == 0 {
			break
		}
		s--
		d--
		for i := 0; i < 200; i++ {
			for j := 0; j < 200; j++ {
				pass[i][j] = INF
			}
		}
		for i := 0; i < 200; i++ {
			pass[i][i] = 0
		}
		for i := 0; i < m; i++ {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			a, _ := strconv.Atoi(buf_[0])
			b, _ := strconv.Atoi(buf_[1])
			f, _ := strconv.Atoi(buf_[2])
			a--
			b--
			pass[a][b] = f
			pass[b][a] = f
		}
		fmt.Println(dijkstra(s, d, c, n))
	}
}

func dijkstra(s, g, c, n int) float64 {
	d := make([][]float64, 200)
	used := make([][]bool, 200)
	for i := 0; i < 200; i++ {
		d[i] = make([]float64, 20)
		used[i] = make([]bool, 20)
	}
	for i := range d {
		for j := range d[i] {
			d[i][j] = INF
		}
	}
	d[s][c] = 0
	for {
		v := -1
		w := -1
		for u := 0; u < n; u++ {
			for i := 0; i < c+1; i++ {
				if !used[u][i] && (v == -1 || d[u][i] < d[v][w]) {
					v = u
					w = i
				}
			}
		}
		if v == -1 {
			break
		}
		used[v][w] = true
		for u := 0; u < n; u++ {
			d[u][w] = math.Min(d[u][w], d[v][w]+float64(pass[v][u]))
			if w-1 >= 0 && pass[v][u] != INF {
				d[u][w-1] = math.Min(d[u][w-1], d[v][w]+(float64(pass[v][u]/2.0)))
			}
		}
	}
	ret := float64(INF)
	for i := 0; i < c+1; i++ {
		ret = math.Min(ret, d[g][i])
	}
	return ret
}

C++: #include<iostream>
#include<map>
#include<cstdio>
#include<vector>
#include<algorithm>
#include<queue>
using namespace std;
typedef pair< int ,int > P;
typedef pair< int , P > road;
main(){
  while(1){
    int c,n,m,s,d;
    int a,b,f;
    vector< P > bus[120];
    int min_cost[120];
    queue< road > que;
    road r;
    P p;
    cin>>c>>n>>m>>s>>d;//c waribiki n mati m rosen s start d goal
    if(c==0&&n==0&&m==0&&s==0&&d==0)break;
    for(int i=1;i<=n;i++){
      min_cost[i]=1<<21;
    }
    for(int i=0;i<m;i++){
      cin>>a>>b>>f;
      p.first=b;
      p.second=f;
      bus[a].push_back(p);
      p.first=a;
      p.second=f;
      bus[b].push_back(p);
    }
    r.first=c;
    r.second.first=s;
    r.second.second=0;
    que.push(r);
    while(!que.empty()){
      road now=que.front();
      int size=bus[now.second.first].size();
      for(int i=0;i<size;i++){
	if(bus[now.second.first][i].second+now.second.second<min_cost[bus[now.second.first][i].first]){
	  min_cost[bus[now.second.first][i].first]=bus[now.second.first][i].second+now.second.second;
	  r.first=now.first;
	  r.second.first=bus[now.second.first][i].first;
	  r.second.second=bus[now.second.first][i].second+now.second.second;
	  que.push(r);
	}
	if(now.first!=0&&bus[now.second.first][i].second/2+now.second.second<min_cost[bus[now.second.first][i].first]){
	  min_cost[bus[now.second.first][i].first]=bus[now.second.first][i].second/2+now.second.second;
	  r.first=now.first-1;
	  r.second.first=bus[now.second.first][i].first;
	  r.second.second=bus[now.second.first][i].second/2+now.second.second;
	  que.push(r); 
	}
      }  
      que.pop();
    }
    while(!que.empty()){
      que.pop();
    }
    cout<<min_cost[d]<<endl;
  }
}

C++: #include<cstdio>
#include<iostream>
#include<vector>
#include<queue>
using namespace std;
#define INF 1e+8
class Data {
public:
	int to,cost,num;
	Data(){}
	Data(int to, int cost, int num):to(to),cost(cost),num(num){}
	bool operator<(const Data &s) const {
		if(cost != s.cost) return cost > s.cost;
		return to < s.to;
	}
};

int main() {
	int c,n,m,s,g;
	while(scanf("%d%d%d%d%d",&c,&n,&m,&s,&g),(c|n|m|s|g)) {
		vector<Data> G[128];
		for(int i = 0; i < m; i++) {
			int a,b,f;
			scanf("%d%d%d",&a,&b,&f);
			G[a].push_back(Data(b,f,0));
			G[b].push_back(Data(a,f,0));
		}
		priority_queue<Data> Q;
		Q.push(Data(s,0,c));
		int ans = -1;
		while(!Q.empty()) {
			Data e = Q.top();Q.pop();
			int v = e.to;
			if(v == g) {
				ans = e.cost;
				break;
			}
			for(int i = 0; i < G[v].size(); i++) {
				Data E = G[v][i];
				if(e.num != 0) {
					Q.push(Data(E.to,E.cost/2 + e.cost,e.num-1));
				}
				Q.push(Data(E.to,E.cost + e.cost,e.num));
			}
		}
		printf("%d\n",ans);
	}
	return 0;
}

C++: #include<iostream>
#include<queue>
#include<vector>
using namespace std;
typedef pair<int, int> P;
typedef pair<P, int> PP;
int c,n,m,s,d;
vector<P> G[101];
int cost[101][11];
int INF=10000000;

int dijkstra(int s){
	priority_queue<PP, vector<PP>, greater<PP> >que;
	for(int i=0;i<=100;i++){
		for(int j=0;j<=10;j++){
			cost[i][j]=INF;
		}
	}
	cost[s][0]=0;
	que.push(PP(P(s,0),0));
	while(que.size()){
		PP p=que.top();que.pop();
		int v=p.first.first,d=p.first.second,k=p.second;
		if(cost[v][k]<d)continue;
		for(int i=0;i<G[v].size();i++){
			P e=G[v][i];
			if(cost[e.first][k]>cost[v][k]+e.second){
				cost[e.first][k]=cost[v][k]+e.second;
				que.push(PP(P(e.first,cost[e.first][k]),k));
			}
		}
		if(k<c)for(int i=0;i<G[v].size();i++){
			P e=G[v][i];
			if(cost[e.first][k+1]>cost[v][k]+e.second/2){
				cost[e.first][k+1]=cost[v][k]+e.second/2;
				que.push(PP(P(e.first,cost[e.first][k+1]),k+1));
			}
		}
	}

	int ans=INF;
	for(int i=0;i<=10;i++){
		ans=min(ans,cost[d][i]);
	}
	return ans;
}

int main(void){
	while(1){
		scanf("%d%d%d%d%d",&c,&n,&m,&s,&d);
		if(c==0 && n==0 && m==0 && s==0 && d==0)break;
		for(int i=0;i<=100;i++)G[i].clear();
		for(int i=0;i<m;i++){
			int a,b,f;
			scanf("%d%d%d",&a,&b,&f);
			G[a].push_back(P(b,f));
			G[b].push_back(P(a,f));
		}
		cout << dijkstra(s) << endl;
	}
    return 0;
}

C++: #include <bits/stdc++.h>
#include<stdio.h>
using namespace std;
#define FOR(i,k,n) for(int i = (k); i < (n); i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(a) begin(a),end(a)
#define MS(m,v) memset(m,v,sizeof(m))
#define D10  fixed<<setprecision(10)
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> P;
typedef long long ll;
const ll INF = 114514810;
const ll MOD = 1000000007;
const double EPS = 1e-8;
const double PI = acos(-1.0);
struct edge
{
	int from, to, cost;
	bool operator < (const edge& e) const { return cost < e.cost; }
	bool operator >(const edge& e) const { return cost > e.cost; }
};
int dx[] = { -1, 0, 0, 1 }; int dy[] = { 0, -1, 1, 0 };
bool valid(int x, int y, int h, int w) { return (x >= 0 && y >= 0 && x < h&&y < w); }
///*************************************************************************************///
///*************************************************************************************///
///*************************************************************************************///

int d[2000];
vector<vector<edge>> es;

void dijkstra(int s)
{
	fill(ALL(d), INF);
	d[s] = 0;
	priority_queue<P, vector<P>, greater<P>> que;
	que.push(P(0, s));
	while (!que.empty())
	{
		P p = que.top(); que.pop();
		int v = p.second;
		if (d[v] < p.first) continue;
		REP(i, es[v].size())
		{
			edge e = es[v][i];
			if (d[e.to] > d[v] + e.cost)
			{
				d[e.to] = d[v] + e.cost;
				que.push(P(d[e.to], e.to));
			}
		}
	}
}

int main()
{
	int c, n, m, s, g;
	while (cin >> c >> n >> m >> s >> g, c)
	{
		s--; g--;
		es.clear();
		es.resize(c*n+n);
		REP(i, m)
		{
			int a, b, f;
			cin >> a >> b >> f;
			a--; b--;
			REP(j, c+1) es[a + j*n].push_back(edge{ a + j*n, b + j*n, f });
			REP(j, c) es[a + (j+1)*n].push_back(edge{ a + (j+1)*n, b + j*n, f/2 });
			REP(j, c + 1) es[b + j*n].push_back(edge{ b + j*n, a + j*n, f });
			REP(j, c) es[b + (j + 1)*n].push_back(edge{ b + (j + 1)*n, a + j*n, f / 2 });
		}
		dijkstra(s + c*n);
		int ans = INF;
		REP(i, c + 1) ans = min(ans, d[g + i*n]);
		cout << ans << endl;
	}

	return 0;
}