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<bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
typedef pair<int, pii> piii;//cost, v, ticket
struct edge{
  int to, cost;
};

int main(int argc, char *argv[]){
  int c, n, m, s, d;
  while(std::cin >> c >> n >> m >> s >> d, n){
    s--;d--;
    vector<vector<edge> > g(n);
    for (int i = 0; i < m; i++) {
      edge e;
      int from;
      std::cin >> from >> e.to >> e.cost;
      e.to--;from--;
      g[from].push_back(e);
      g[e.to].push_back((edge){from, e.cost});
    }
    vector<vector<int> > dp(c + 1, vector<int>(n, 1e9));
    dp[0][s] = 0;
    priority_queue<piii, vector<piii>, greater<piii> > que;
    que.push(piii(0, pii(s, 0)));
    while(!que.empty()){
      int cost   = que.top().first;
      int v      = que.top().second.first;
      int ticket = que.top().second.second;
      que.pop();
      for (int i = 0; i < g[v].size(); i++) {
        edge e = g[v][i];
        if(dp[ticket][e.to] > dp[ticket][v] + e.cost){
          dp[ticket][e.to] = dp[ticket][v] + e.cost;
          que.push(piii(dp[ticket][e.to], pii(e.to, ticket)));
        }
        if(ticket + 1 <= c &&
           dp[ticket + 1][e.to] > dp[ticket][v] + e.cost/2){
          dp[ticket + 1][e.to] = dp[ticket][v] + e.cost/2;
          que.push(piii(dp[ticket + 1][e.to],
                        pii(e.to, ticket + 1)));
        }
      }
    }
    int ans = 1e9;
    for (int i = 0; i < c; i++) {
      ans = min(ans, dp[i][d]);
    }
    std::cout << ans << std::endl;
  }
  return 0;
}

C++: #include <iostream>
#include <algorithm>

using namespace std;

const int inf = 999999;

int func(int dir[101][101], int c, int n, int s, int t)
{
	int r = inf;
	int dp[1<<10+1][101];
	fill(&dp[0][0], &dp[1<<10][100], inf);
	
	dp[(1<<c)-1][s] = 0;
	for(int i = (1<<c)-1; i >= 0; i--){
		r = min(r, dp[i][t]);
		for(int j = 1; j <= n; j++){
			for(int k = 0; k < c; k++){
				if(i >> k & 1){
					for(int l = 1; l <= n; l++){
						if(dp[j][l] >= 0){
							dp[i& ~(1 << k)][l] = min(dp[i & ~(1<<k)][l], (dp[i][j]+dir[j][l]/2));
						}
					}
				}
			}
		}
	}
	
	return r;
}

int main()
{
	int c, n, m, s, d, a, b, f;
	int dir[101][101];
	
	while(cin>>c>>n>>m>>s>>d && c && n && m && s && d){
		fill(&dir[0][0], &dir[100][100], inf);
		for(int i = 0; i <= 100; i++){
			dir[i][i] = 0;
		}
		while(m--){
			cin >> a >> b >> f;
			dir[a][b] = dir[b][a] = f;
		}
		
		cout << func(dir, c, n, s, d) << endl;
	}
	
	return 0;
}

C++: #include<iostream>
using namespace std;
#include<vector>
#include<queue>
#include<math.h>
struct crq{
	int cost;
	int ticket;
	int now;

	bool operator >(const crq& p) const{
	return cost > p.cost;
	}
};//cost root que
struct root{
	int s;
	int g;
	int cost;
};

priority_queue<crq,vector<crq>,greater<crq>> q;
vector<root> vr;
int c;
int n;
int m;
int s;
int d;
int ans;
bool townSearched[100];
unsigned int townMin[100][11];
int main(){
	while(cin>>c>>n>>m>>s>>d, c|n|m|s|d){
		vr.clear();
		ans=INT_MAX;
		while(!q.empty())q.pop();
		for(int  i=0;i<100;i++){
			townSearched[i]=false;
			for(int  j=0;j<11;j++)townMin[i][j]=INT_MAX;
		}
		for(int i=0;i<m;i++){
			root r;
			cin>>r.s;
			r.s--;
			cin>>r.g;
			r.g--;
			cin>>r.cost;
			vr.push_back(r);
		}
		townMin[s-1][c]=0;
		crq start;
		start.cost=0;
		start.ticket=c;
		start.now=s-1;
		q.push(start);
		while(1){
			crq crq2=q.top();q.pop();
			if(crq2.now==d-1){
				ans=crq2.cost;
				break;
			}
			

			for(int i=0;i<m;i++){
				if(vr.at(i).s==crq2.now){
					if(!townSearched[vr.at(i).g]&&townMin[vr.at(i).g][crq2.ticket]>crq2.cost+vr.at(i).cost){
						crq add;
						add.cost=crq2.cost+vr.at(i).cost;
						add.ticket=crq2.ticket;
						add.now=vr.at(i).g;
						townMin[vr.at(i).g][crq2.ticket]=crq2.cost+vr.at(i).cost;
						q.push(add);
					}

					if(!townSearched[vr.at(i).g]&&crq2.ticket>0&&townMin[vr.at(i).g][crq2.ticket-1]>crq2.cost+vr.at(i).cost/2){
						crq add;
						add.cost=crq2.cost+vr.at(i).cost/2;
						add.ticket=crq2.ticket-1;
						add.now=vr.at(i).g;
						townMin[vr.at(i).g][crq2.ticket]=crq2.cost+vr.at(i).cost/2;
						q.push(add);
					}

				}
				if(vr.at(i).g==crq2.now){
					if(!townSearched[vr.at(i).s]&&townMin[vr.at(i).s][crq2.ticket]>crq2.cost+vr.at(i).cost){
						crq add;
						add.cost=crq2.cost+vr.at(i).cost;
						add.ticket=crq2.ticket;
						add.now=vr.at(i).s;
						townMin[vr.at(i).s][crq2.ticket]=crq2.cost+vr.at(i).cost;
						q.push(add);
					}

					if(!townSearched[vr.at(i).s]&&crq2.ticket>0&&townMin[vr.at(i).s][crq2.ticket-1]>crq2.cost+vr.at(i).cost/2){
						crq add;
						add.cost=crq2.cost+vr.at(i).cost/2;
						add.ticket=crq2.ticket-1;
						add.now=vr.at(i).s;
						townMin[vr.at(i).s][crq2.ticket]=crq2.cost+vr.at(i).cost/2;
						q.push(add);
					}

				}
			}
			townSearched[crq2.now]=true;
		}
		cout<<ans<<endl;
	}
	return 0;
}